diff --git a/app/containers/message/Components/Attachments/CollapsibleQuote/index.tsx b/app/containers/message/Components/Attachments/CollapsibleQuote/index.tsx
index 073e5d7660d..f84df0aefdc 100644
--- a/app/containers/message/Components/Attachments/CollapsibleQuote/index.tsx
+++ b/app/containers/message/Components/Attachments/CollapsibleQuote/index.tsx
@@ -1,4 +1,3 @@
-import { transparentize } from 'color2k';
 import { dequal } from 'dequal';
 import React, { useContext, useState } from 'react';
 import { StyleSheet, Text, View } from 'react-native';
@@ -13,6 +12,7 @@ import Markdown from '../../../../markdown';
 import MessageContext from '../../../Context';
 import Touchable from '../../../Touchable';
 import { BUTTON_HIT_SLOP } from '../../../utils';
+import withAlpha from '../../../../../lib/helpers/withAlpha';
 
 const styles = StyleSheet.create({
 	button: {
@@ -144,7 +144,7 @@ const CollapsibleQuote = React.memo(
 
 		try {
 			if (attachment.color) {
-				backgroundColor = transparentize(attachment.color, 0.8);
+				backgroundColor = withAlpha(attachment.color, 0.8); // works for rgba, rgb, hex (#rgb, #rrggbb)
 				strokeExtraLight = attachment.color;
 				strokeLight = attachment.color;
 				strokeMedium = attachment.color;
diff --git a/app/lib/helpers/withAlpha.test.ts b/app/lib/helpers/withAlpha.test.ts
new file mode 100644
index 00000000000..fcc6daaebca
--- /dev/null
+++ b/app/lib/helpers/withAlpha.test.ts
@@ -0,0 +1,31 @@
+import withAlpha from './withAlpha';
+
+describe('withAlpha', () => {
+	test('rgba to be rgba with updated alpha', () => {
+		expect(withAlpha('rgba(255, 0, 0, 0.2)', 0.8)).toBe('rgba(255, 0, 0, 0.8)');
+	});
+
+	test('rgb to be rgba with updated alpha', () => {
+		expect(withAlpha('rgb(255, 0, 0)', 0.8)).toBe('rgba(255, 0, 0, 0.8)');
+	});
+
+	test('hex #rgb to be hex #rrggbbaa with updated alpha', () => {
+		expect(withAlpha('#f00', 0.8)).toBe('#ff0000cc');
+	});
+
+	test('hex #rrggbb to be hex #rrggbbaa with updated alpha', () => {
+		expect(withAlpha('#ff0000', 0.8)).toBe('#ff0000cc');
+	});
+
+	test('hex #rrggbbaa to be hex #rrggbbaa with updated alpha', () => {
+		expect(withAlpha('#ff000022', 0.8)).toBe('#ff0000cc');
+	});
+
+	test("'red' to be 'red' without change in alpha", () => {
+		expect(withAlpha('red', 0.8)).toBe('red');
+	});
+
+	test('hsl to be hsl without change in alpha', () => {
+		expect(withAlpha('hsl(0, 100%, 50%)', 0.8)).toBe('hsl(0, 100%, 50%)');
+	});
+});
diff --git a/app/lib/helpers/withAlpha.ts b/app/lib/helpers/withAlpha.ts
new file mode 100644
index 00000000000..4fb5f4ffcdf
--- /dev/null
+++ b/app/lib/helpers/withAlpha.ts
@@ -0,0 +1,78 @@
+/**
+ * Applies an alpha (opacity) value to a color string.
+ *
+ * Supported formats:
+ * - `rgba(r,g,b,a)` → updates alpha
+ * - `rgb(r,g,b)` → converted to `rgba`
+ * - `#rgb`, `#rrggbb`, `#rrggbbaa` → normalized to `#rrggbbaa`
+ *
+ * Unsupported formats (returned unchanged):
+ * - Named colors (`red`)
+ * - `hsl()` / `hsla()`
+ * - Invalid color strings
+ *
+ * @param color Input color string
+ * @param transparency Transparency value between `0` and `1` (default: `0`)
+ */
+const withAlpha = (color: string, transparency: number = 0) => {
+	if (!color) {
+		return color;
+	}
+
+	const alpha = 1 - transparency;
+
+	// case rgba
+	if (color.startsWith('rgba')) {
+		const match = color.match(/rgba\(\s*(\d+)\s*,\s*(\d+)\s*,\s*(\d+)\s*,\s*([0-9.]+)\s*\)/);
+
+		if (!match) {
+			return color;
+		}
+
+		const [, r, g, b] = match;
+		return `rgba(${r}, ${g}, ${b}, ${alpha})`;
+	}
+
+	// case rgb
+	if (color.startsWith('rgb')) {
+		const match = color.match(/rgb\(\s*(\d+)\s*,\s*(\d+)\s*,\s*(\d+)\s*\)/);
+
+		if (!match) {
+			return color;
+		}
+
+		const [, r, g, b] = match;
+		return `rgba(${r}, ${g}, ${b}, ${alpha})`;
+	}
+
+	// case hex
+	if (color.startsWith('#')) {
+		let hex = color.slice(1);
+
+		// #rgb → #rrggbb
+		if (hex.length === 3) {
+			hex = hex
+				.split('')
+				.map(c => c + c)
+				.join('');
+		}
+
+		if (hex.length === 8) {
+			hex = hex.substring(0, 6);
+		}
+		if (hex.length !== 6) {
+			return color;
+		}
+
+		const alphaHex = Math.round(alpha * 255)
+			.toString(16)
+			.padStart(2, '0');
+
+		return `#${hex}${alphaHex}`;
+	}
+
+	// named colors / invalid strings
+	return color;
+};
+
+export default withAlpha;
diff --git a/package.json b/package.json
index 45c7b5e50e1..2508135c886 100644
--- a/package.json
+++ b/package.json
@@ -52,7 +52,6 @@
 		"@rocket.chat/sdk": "RocketChat/Rocket.Chat.js.SDK#mobile",
 		"@rocket.chat/ui-kit": "0.31.19",
 		"bytebuffer": "5.0.1",
-		"color2k": "1.2.4",
 		"dayjs": "^1.11.18",
 		"dequal": "2.0.3",
 		"ejson": "2.2.3",
diff --git a/yarn.lock b/yarn.lock
index 5f334cbad37..44b5ad84f64 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -7000,11 +7000,6 @@ color-string@^1.9.0:
     color-name "^1.0.0"
     simple-swizzle "^0.2.2"
 
-color2k@1.2.4:
-  version "1.2.4"
-  resolved "https://registry.yarnpkg.com/color2k/-/color2k-1.2.4.tgz#af34950ac58e23cf224a01cb8dd0c9911a79605e"
-  integrity sha512-DiwdBwc0BryPFFXoCrW8XQGXl2rEtMToODybxZjKnN5IJXt/tV/FsN02pCK/b7KcWvJEioz3c74lQSmayFvS4Q==
-
 color@^4.2.3:
   version "4.2.3"
   resolved "https://registry.yarnpkg.com/color/-/color-4.2.3.tgz#d781ecb5e57224ee43ea9627560107c0e0c6463a"