diff --git a/src/CSS.php b/src/CSS.php
index 77465ea..4f56320 100644
--- a/src/CSS.php
+++ b/src/CSS.php
@@ -583,12 +583,13 @@ protected function convertLegacyColors($content)
         */
 
         // convert legacy color syntax
-        $content = preg_replace('/(rgb|hsl)a?\(([^,\s]+)\s*,\s*([^,\s]+)\s*,\s*([^,\s]+)\s*,\s*([^\s\)]+)\)/i', '$1($2 $3 $4 / $5)', $content);
-        $content = preg_replace('/(rgb|hsl)a?\(([^,\s]+)\s*,\s*([^,\s]+)\s*,\s*([^,\s]+)\)/i', '$1($2 $3 $4)', $content);
+        $content = preg_replace('/(rgb)a?\(\s*([0-9]{1,3}%?)\s*,\s*([0-9]{1,3}%?)\s*,\s*([0-9]{1,3}%?)\s*,\s*([0,1]?(?:\.[0-9]*)?)\s*\)/i', '$1($2 $3 $4 / $5)', $content);
+        $content = preg_replace('/(rgb)a?\(\s*([0-9]{1,3}%?)\s*,\s*([0-9]{1,3}%?)\s*,\s*([0-9]{1,3}%?)\s*\)/i', '$1($2 $3 $4)', $content);
+        $content = preg_replace('/(hsl)a?\(\s*([0-9]+(?:deg|grad|rad|turn)?)\s*,\s*([0-9]{1,3}%)\s*,\s*([0-9]{1,3}%)\s*,\s*([0,1]?(?:\.[0-9]*)?)\s*\)/i', '$1($2 $3 $4 / $5)', $content);
+        $content = preg_replace('/(hsl)a?\(\s*([0-9]+(?:deg|grad|rad|turn)?)\s*,\s*([0-9]{1,3}%)\s*,\s*([0-9]{1,3}%)\s*\)/i', '$1($2 $3 $4)', $content);
 
         // convert `rgb` to `hex`
-        $dec = '([01]?[0-9]?[0-9]|2[0-4][0-9]|25[0-5])'; // [000-255] THX @ https://www.regular-expressions.info/numericranges.html
-
+        $dec = '([01]?[0-9]?[0-9]|2[0-4][0-9]|25[0-5])';
         return preg_replace_callback(
             "/rgb\($dec $dec $dec\)/i",
             function ($match) {
@@ -620,10 +621,10 @@ protected function cleanupModernColors($content)
         $tag = '(rgb|hsl|hwb|(?:(?:ok)?(?:lch|lab)))';
 
         // remove alpha channel if it's pointless ..
-        $content = preg_replace('/' . $tag . '\(([^\s]+)\s+([^\s]+)\s+([^\s]+)\s+\/\s+1(?:[\.\d]*|00%)?\)/i', '$1($2 $3 $4)', $content);
+        $content = preg_replace('/' . $tag . '\(\s*([^\s]+)\s+([^\s]+)\s+([^\s]+)\s+\/\s+1(?:(?:\.\d?)*|00%)?\s*\)/i', '$1($2 $3 $4)', $content);
 
         // replace `transparent` with shortcut ..
-        $content = preg_replace('/' . $tag . '\([^\s]+\s+[^\s]+\s+[^\s]+\s+\/\s+0(?:[\.0%]*)?\)/i', '#fff0', $content);
+        $content = preg_replace('/' . $tag . '\(\s*[^\s]+\s+[^\s]+\s+[^\s]+\s+\/\s+0(?:[\.0%]*)?\s*\)/i', '#fff0', $content);
 
         return $content;
     }
diff --git a/tests/CSS/CSSTest.php b/tests/CSS/CSSTest.php
index 25f6b07..0046c4e 100644
--- a/tests/CSS/CSSTest.php
+++ b/tests/CSS/CSSTest.php
@@ -860,6 +860,23 @@ public static function dataProvider()
             'background-position:right .8em bottom calc(50% - 5px),right .8em top calc(50% - 5px);',
         );
 
+        // https://github.com/matthiasmullie/minify/issues/422
+        $tests[] = array(
+            'a {
+                color: rgba(var(--bs-link-color-rgb),var(--bs-link-opacity,1));
+                text-decoration: none;
+            }
+            a:hover {
+                --bs-link-color-rgb: var(--bs-link-hover-color-rgb);
+            }
+            a:not([href]):not([class]),
+            a:not([href]):not([class]):hover {
+                color: inherit;
+                text-decoration: none;
+            }',
+            'a{color:rgba(var(--bs-link-color-rgb),var(--bs-link-opacity,1));text-decoration:none}a:hover{--bs-link-color-rgb:var(--bs-link-hover-color-rgb)}a:not([href]):not([class]),a:not([href]):not([class]):hover{color:inherit;text-decoration:none}',
+        );
+
         return $tests;
     }