diff --git a/firestore.rules b/firestore.rules
index fc8ee76..e8f070f 100644
--- a/firestore.rules
+++ b/firestore.rules
@@ -61,11 +61,12 @@ service cloud.firestore {
 
 			function verifyFieldTypes() {
 				return verifyBoolType("sound") &&
+					verifyBoolType("coloredEdges") &&
 					verifyThemeValue();
 			}
 
 			function getPossibleFields() {
-				let requiredFields = ["sound", "theme"];
+				let requiredFields = ["sound", "theme", "coloredEdges"];
 				let optionalFields = [];
 				let allFields = requiredFields.concat(optionalFields);
 				return [requiredFields, allFields];
diff --git a/functions/index.js b/functions/index.js
index f99cbc3..6e8df5b 100644
--- a/functions/index.js
+++ b/functions/index.js
@@ -33,6 +33,7 @@ exports.userCreated = functions.auth.user().onCreate((user) => {
 		return db.collection("users").doc(user.uid).set({
 			sound: true,
 			theme: "default",
+			coloredEdges: false,
 		});
 	});
 });
diff --git a/src/App.js b/src/App.js
index c4bae5d..3a46891 100644
--- a/src/App.js
+++ b/src/App.js
@@ -121,6 +121,7 @@ class App extends React.Component {
       userDataPresent: false,
       sound: true,
       theme: "default",
+      coloredEdges: false,
       pageLoading: true,
     };
     
@@ -161,9 +162,11 @@ class App extends React.Component {
           .then((userDoc) => {
             newState.sound = userDoc.data().sound;
             newState.theme = userDoc.data().theme;
+            newState.coloredEdges = userDoc.data().coloredEdges;
           }).catch((error) => {
             newState.sound = true;
             newState.theme = "default";
+            newState.coloredEdges = false;
           });
       }
       
@@ -234,6 +237,17 @@ class App extends React.Component {
     });
   }
 
+  handleColoredEdgesChange = (newColoredEdges, globalChange = false) => {
+    if (globalChange) firebase.firestore().collection("users")
+      .doc(this.state.user.uid)
+      .update({
+        coloredEdges: newColoredEdges,
+      });
+    this.setState({
+      coloredEdges: newColoredEdges,
+    });
+  }
+
   acceptCookies = () => {
     window.removeEventListener('resize', this.updateCookieNoticeMargins);
     this.cookieNoticeHeight = this.cookieNotice.offsetHeight;
@@ -285,10 +299,14 @@ class App extends React.Component {
                   <GroupPage db={db} functions={functions} user={this.state.user} logEvent={analytics.logEvent} page={this.page} />
                 </Route>
                 <Route path="/settings">
-                  <Settings db={db} user={this.state.user} sound={this.state.sound} handleSoundChange={this.handleSoundChange} theme={this.state.theme} handleThemeChange={this.handleThemeChange} themes={themes} logEvent={analytics.logEvent} page={this.page} />
+                  <Settings db={db} user={this.state.user} sound={this.state.sound} coloredEdges={this.state.coloredEdges} handleColoredEdgesChange={this.handleColoredEdgesChange} handleSoundChange={this.handleSoundChange} theme={this.state.theme} handleThemeChange={this.handleThemeChange} themes={themes} logEvent={analytics.logEvent} page={this.page} />
                 </Route>
                 <Route path="/progress/:progressId" exact>
-                  <Progress db={db} functions={functions} user={this.state.user} sound={this.state.sound} handleSoundChange={this.handleSoundChange} theme={this.state.theme} handleThemeChange={this.handleThemeChange} themes={themes} logEvent={analytics.logEvent} page={this.page} />
+                  <Progress db={db} functions={functions} user={this.state.user} sound={this.state.sound} coloredEdges={this.state.coloredEdges} handleColoredEdgesChange={this.handleColoredEdgesChange} handleSoundChange={this.handleSoundChange} theme={this.state.theme} handleThemeChange={this.handleThemeChange} themes={themes} logEvent={analytics.logEvent} page={this.page} />
+                  {
+                    this.state.coloredEdges &&
+                    <div className="colored-edges"></div>
+                  }
               </Route>
                 <Route path="/create-set" exact>
                   <CreateSet db={db} user={this.state.user} logEvent={analytics.logEvent} page={this.page} />
diff --git a/src/Progress.js b/src/Progress.js
index 8a5f4d6..7400d89 100644
--- a/src/Progress.js
+++ b/src/Progress.js
@@ -61,6 +61,7 @@ export default withRouter(class Progress extends React.Component {
 			showSettings: false,
 			soundInput: this.props.sound,
 			themeInput: this.props.theme,
+			coloredEdgesInput: this.props.coloredEdges,
 			setIds: [],
 			attemptNumber: 1,
 			attemptHistory: {},
@@ -232,9 +233,16 @@ export default withRouter(class Progress extends React.Component {
 		});
 	}
 
+	handleColoredEdgesInputChange = (event) => {
+		this.setState({
+			coloredEdgesInput: event.target.checked,
+		});
+	}
+
 	saveSettings = (globalChange) => {
 		this.props.handleSoundChange(this.state.soundInput, globalChange);
 		this.props.handleThemeChange(this.state.themeInput, globalChange);
+		this.props.handleColoredEdgesChange(this.state.coloredEdgesInput, globalChange);
 		this.hideSettings();
 	}
 
@@ -702,9 +710,11 @@ export default withRouter(class Progress extends React.Component {
 									saveSettings={this.saveSettings}
 									handleSoundInputChange={this.handleSoundInputChange}
 									handleThemeInputChange={this.handleThemeInputChange}
+									handleColoredEdgesInputChange={this.handleColoredEdgesInputChange}
 									themes={this.props.themes}
 									soundInput={this.state.soundInput}
 									themeInput={this.state.themeInput}
+									coloredEdgesInput={this.state.coloredEdgesInput}
 								/>
 
 
diff --git a/src/Settings.js b/src/Settings.js
index 804f09a..cd91892 100644
--- a/src/Settings.js
+++ b/src/Settings.js
@@ -22,6 +22,7 @@ export default withRouter(class Settings extends Component {
 			],
 			soundInput: this.props.sound,
 			themeInput: this.props.theme,
+			coloredEdgesInput: this.props.coloredEdges,
 		};
 
 		let isMounted = true;
@@ -60,9 +61,16 @@ export default withRouter(class Settings extends Component {
 		});
 	}
 
+	handleColoredEdgesInputChange = (event) => {
+		this.setState({
+			coloredEdgesInput: event.target.checked,
+		});
+	}
+
 	saveSettings = (globalChange) => {
 		this.props.handleSoundChange(this.state.soundInput, globalChange);
 		this.props.handleThemeChange(this.state.themeInput, globalChange);
+		this.props.handleColoredEdgesChange(this.state.coloredEdgesInput, globalChange);
 		this.props.history.push("/");
 	}
 
@@ -77,9 +85,11 @@ export default withRouter(class Settings extends Component {
 						saveSettings={this.saveSettings}
 						handleSoundInputChange={this.handleSoundInputChange}
 						handleThemeInputChange={this.handleThemeInputChange}
+						handleColoredEdgesInputChange={this.handleColoredEdgesInputChange}
 						themes={this.props.themes}
 						soundInput={this.state.soundInput}
 						themeInput={this.state.themeInput}
+						coloredEdgesInput={this.state.coloredEdgesInput}
 					/>
 
 					<div className="settings-save-container">
diff --git a/src/SettingsContent.js b/src/SettingsContent.js
index f677a34..9fe143e 100644
--- a/src/SettingsContent.js
+++ b/src/SettingsContent.js
@@ -10,17 +10,27 @@ export default class SettingsContent extends Component {
 		return (
 			<>
 				<h1 className="settings-header">Settings</h1>
-				<label className="settings-sound-container">
-					<Checkbox
-						checked={this.props.soundInput}
-						onChange={this.props.handleSoundInputChange}
-						inputProps={{ 'aria-label': 'checkbox' }}
-					/>
-					<span>Sound</span>
-				</label>
+				<div className="settings-options-container">
+					<label>
+						<Checkbox
+							checked={this.props.soundInput}
+							onChange={this.props.handleSoundInputChange}
+							inputProps={{ 'aria-label': 'checkbox' }}
+						/>
+						<span>Sound</span>
+					</label>
+					<label>
+						<Checkbox
+							checked={this.props.coloredEdgesInput}
+							onChange={this.props.handleColoredEdgesInputChange}
+							inputProps={{ 'aria-label': 'checkbox' }}
+						/>
+						<span>Coloured edges</span>
+					</label>
+				</div>
 
 				<h2 className="settings-theme-header">Theme</h2>
-				<div className="settings-themes-container">
+				<div className="settings-options-container">
 					{
 						this.props.themes.map((theme) =>
 							<Button
diff --git a/src/css/App.css b/src/css/App.css
index 96a06ad..200b196 100644
--- a/src/css/App.css
+++ b/src/css/App.css
@@ -6,7 +6,8 @@ html {
   --background-color: #111111;
   --background-color-dark: #000000;
   --overlay-color: #333333;
-  background-color: var(--background-color);
+
+  height: 100%;
   color: var(--text-color);
 
   --default: #2a8c8c;
@@ -112,10 +113,6 @@ html {
   --primary-color-dark: var(--orange-dark);
 }
 
-html {
-  height: 100%;
-}
-
 body {
   max-width: 1080px;
   margin: auto;
@@ -126,6 +123,7 @@ body, #root, #root > div, #root > div > div:first-child {
   display: flex;
   flex-direction: column;
   flex: 1;
+  background-color: var(--background-color);
 }
 
 main {
@@ -409,6 +407,18 @@ label .MuiIconButton-label > input {
   opacity: 0 !important;
 }
 
+.colored-edges {
+	z-index: -5;
+	background-color: var(--primary-color-dark);
+	position: fixed;
+	top: 0;
+	left: 0;
+	width: 100vw;
+	height: 100vh;
+  opacity: 0.7;
+}
+
+
 @media screen and (max-width: 420px) {
   .progress-history-container > div > *:nth-child(2), .progress-history-container--complete > div > *:nth-last-child(3), .progress-history-container--incomplete > div > *:nth-last-child(4) {
     display: none;
diff --git a/src/css/SettingsContent.css b/src/css/SettingsContent.css
index 5b188aa..1e46a59 100644
--- a/src/css/SettingsContent.css
+++ b/src/css/SettingsContent.css
@@ -1,4 +1,4 @@
-.settings-themes-container {
+.settings-options-container {
 	display: flex;
 	flex-direction: row;
 	column-gap: 16px;
@@ -7,7 +7,7 @@
 	flex-wrap: wrap;
 }
 
-.settings-header, .settings-sound-container, .settings-themes-container {
+.settings-header, .settings-options-container {
 	margin-bottom: 36px;
 	margin-top: 0;
 }
diff --git a/test/firestore.test.js b/test/firestore.test.js
index 77452a0..e1ca165 100644
--- a/test/firestore.test.js
+++ b/test/firestore.test.js
@@ -51,20 +51,20 @@ describe("Parandum Firestore database", () => {
 
 	it("Can update current user's user collection", async () => {
 		const admin = getAdminFirestore();
-		await admin.collection("users").doc(myId).set({ sound: true });
+		await admin.collection("users").doc(myId).set({ sound: true, theme: "default", coloredEdges: false });
 
 		const db = getFirestore(myAuth);
 		const myTestDoc = db.collection("users").doc(myId);
-		await firebase.assertSucceeds(myTestDoc.update({ sound: false }));
+		await firebase.assertSucceeds(myTestDoc.update({ sound: false, theme: "pink", coloredEdges: true }));
 	});
 
 	it("Can't update current user's user collection with invalid data types", async () => {
 		const admin = getAdminFirestore();
-		await admin.collection("users").doc(myId).set({ sound: true, theme: "default" });
+		await admin.collection("users").doc(myId).set({ sound: true, theme: "default", coloredEdges: false });
 
 		const db = getFirestore(myAuth);
 		const myTestDoc = db.collection("users").doc(myId);
-		await firebase.assertFails(myTestDoc.update({ sound: 0, theme: 0 }));
+		await firebase.assertFails(myTestDoc.update({ sound: 0, theme: 0, coloredEdges: 0 }));
 	});
 
 	it("Can't update current user's user collection with invalid fields", async () => {