diff --git a/src/plugins/cursor-plugin.js b/src/plugins/cursor-plugin.js
index 1bbbdc6..3de0beb 100644
--- a/src/plugins/cursor-plugin.js
+++ b/src/plugins/cursor-plugin.js
@@ -10,6 +10,7 @@ import {
 import { yCursorPluginKey, ySyncPluginKey } from './keys.js'
 
 import * as math from 'lib0/math'
+import { setAlphaChannel } from '../utils/colors.js';
 
 /**
  * Default awareness state filter
@@ -49,8 +50,9 @@ export const defaultCursorBuilder = (user) => {
  * @return {import('prosemirror-view').DecorationAttrs}
  */
 export const defaultSelectionBuilder = (user) => {
+  const color = setAlphaChannel(user.color, 0.7);
   return {
-    style: `background-color: ${user.color}70`,
+    style: `background-color: ${color}`,
     class: 'ProseMirror-yjs-selection'
   }
 }
@@ -91,8 +93,8 @@ export const createDecorations = (
       const user = aw.user || {}
       if (user.color == null) {
         user.color = '#ffa500'
-      } else if (!rxValidColor.test(user.color)) {
-        // We only support 6-digit RGB colors in y-prosemirror
+      } else if (!CSS.supports('color', user.color)) {
+        // We only support CSS colors in y-prosemirror
         console.warn('A user uses an unsupported color format', user)
       }
       if (user.name == null) {
diff --git a/src/utils/colors.js b/src/utils/colors.js
new file mode 100644
index 0000000..b2a18c1
--- /dev/null
+++ b/src/utils/colors.js
@@ -0,0 +1,85 @@
+/**
+ * Detects the type of color format specified in the given string
+ * @param {string} color A Hex/RGB/RGBA/HSL/HSLA string
+ * @returns {'HEX'|'RGB'|'HSL'}
+ */
+export const detectColorFormat = (color) => {
+  if (color.startsWith('#')) {
+    return 'HEX'
+  } else if (color.startsWith('rgb')) {
+    return 'RGB'
+  } else if (color.startsWith('hsl')) {
+    return 'HSL'
+  }
+}
+
+/**
+ * Sets the alpha channel of the given color to the specified value
+ * @param {string} color rgb string
+ * @param {number} alphaValue Number ranging from 0 to 1
+ * @return {string} A new rgba string with the alpha channel set to the `alphaValue` parameter
+ */
+export const setRgbAlphaChannel = (color, alphaValue) => {
+  const [r, g, b] = color.match(/\d+/g)
+  return `rgba(${r}, ${g}, ${b}, ${alphaValue})`
+}
+
+/**
+ * Sets the alpha channel of the given color to the specified value
+ * @param {string} color hex string
+ * @param {number} alphaValue Number ranging from 0 to 1
+ * @return {string} A new Hex string with the alpha channel set to the `alphaValue` parameter
+ */
+export const setHexAlphaChannel = (color, alphaValue) => {
+  // Remove any leading '#' from the hex color string
+  color = color.replace(/^#/, '')
+
+  // Check if the hex color has alpha channel
+  if (color.length === 6) {
+    // If alpha channel doesn't exist, add it
+    color += Math.floor(alphaValue * 255).toString(16).padStart(2, '0')
+  } else if (color.length === 8) {
+    // If alpha channel exists, replace it with the new alpha value
+    color = color.slice(0, 6) + Math.floor(alphaValue * 255).toString(16).padStart(2, '0')
+  }
+
+  return '#' + color
+}
+
+/**
+ * Sets the alpha channel of the given color to the specified value
+ * @param {string} color hsl string
+ * @param {number} alphaValue Number ranging from 0 to 1
+ * @return {string} A new hsla string with the alpha channel set to the `alphaValue` parameter
+ */
+export const setHslAlphaChannel = (color, alphaValue) => {
+  // Extract components from the HSLA color string
+  const match = color.match(/hsl[a]?\(\s*(\d+)\s*,\s*(\d+%)\s*,\s*(\d+%)\s*(?:,\s*([\d.]+)\s*)?\)/i)
+  if (!match) {
+    return null // Return null if the input string doesn't match HSLA format
+  }
+
+  const h = parseInt(match[1]) // Hue
+  const s = parseInt(match[2]) // Saturation
+  const l = parseInt(match[3]) // Lightness
+  let a = match[4] ? parseFloat(match[4]) : 1 // Alpha, default to 1 if not provided
+
+  // Update alpha channel with the new value
+  a = alphaValue
+
+  // Return the updated HSLA color string
+  return `hsla(${h}, ${s}%, ${l}%, ${a})`
+}
+
+/**
+ * Sets the Alpha value of Any type of given color string to the specified value
+ * @param {string} color RGB/Hex/HSL color string
+ * @param {*} alphaValue Color value in the same format with the alpha set to `alphaValue`
+ */
+export const setAlphaChannel = (color, alphaValue) => {
+  const colorFormat = detectColorFormat(color)
+
+  if (colorFormat === 'RGB') return setRgbAlphaChannel(color, alphaValue)
+  if (colorFormat === 'HSL') return setHslAlphaChannel(color, alphaValue)
+  if (colorFormat === 'HEX') return setHexAlphaChannel(color, alphaValue)
+}
diff --git a/tests/y-prosemirror.test.js b/tests/y-prosemirror.test.js
index 2eef1ac..04c1faa 100644
--- a/tests/y-prosemirror.test.js
+++ b/tests/y-prosemirror.test.js
@@ -16,6 +16,7 @@ import {
   yUndoPlugin,
   yXmlFragmentToProsemirrorJSON
 } from '../src/y-prosemirror.js'
+import { setRgbAlphaChannel, setHexAlphaChannel, setHslAlphaChannel, setAlphaChannel } from '../src/utils/colors.js'
 import { EditorState, Plugin, TextSelection } from 'prosemirror-state'
 import { EditorView } from 'prosemirror-view'
 import * as basicSchema from 'prosemirror-schema-basic'
@@ -508,3 +509,35 @@ export const testRepeatGenerateProsemirrorChanges300 = tc => {
   checkResult(applyRandomTests(tc, pmChanges, 300, createNewProsemirrorView))
 }
 */
+
+/**
+ * @param {t.TestCase} _tc
+ */
+export const testColorUtils = _tc => {
+  const rgb = 'rgb(42,42,42)'
+  const rgbWithAlpha = setRgbAlphaChannel(rgb, 0.7)
+  t.compare(rgbWithAlpha, 'rgba(42, 42, 42, 0.7)')
+
+  // even if a rgb string has alpha channel, we should replace with a new value
+  const rgbWithReplacedAlpha = setRgbAlphaChannel(rgbWithAlpha, 0.5)
+  t.compare(rgbWithReplacedAlpha, 'rgba(42, 42, 42, 0.5)')
+
+  const hex = '#007bff'
+  const hexWithAlpha = setHexAlphaChannel(hex, 0.7)
+  t.compare(hexWithAlpha, '#007bffb2')
+
+  const hexWithReplacedAlpha = setHexAlphaChannel(hexWithAlpha, 0.5)
+  t.compare(hexWithReplacedAlpha, '#007bff7f')
+
+  const hsl = 'hsl(240, 100%, 50%)'
+  const hslWithAlpha = setHslAlphaChannel(hsl, 0.7)
+  t.compare(hslWithAlpha, 'hsla(240, 100%, 50%, 0.7)')
+
+  const hslWithReplacedAlpha = setHslAlphaChannel(hslWithAlpha, 0.5)
+  t.compare(hslWithReplacedAlpha, 'hsla(240, 100%, 50%, 0.5)')
+
+  // tests for generic function for all three types
+  t.compare(setAlphaChannel(rgb, 0.7), rgbWithAlpha)
+  t.compare(setAlphaChannel(hex, 0.7), hexWithAlpha)
+  t.compare(setAlphaChannel(hsl, 0.7), hslWithAlpha)
+}