Update lib/util.js

Co-authored-by: Aviv Keller <me@aviv.sh>

Author: carlosnaico77

lib/util.js

@@ -209,10 +209,8 @@ function replaceCloseCode(str, closeSeq, openSeq, keepClose) {
   return result + str.slice(lastIndex);
 }
 
-// Matches #RGB or #RRGGBB
-const hexColorRegExp = /^#(?:[0-9a-fA-F]{3}|[0-9a-fA-F]{6})$/;
-// Matches bg#RGB or bg#RRGGBB
-const bgHexColorRegExp = /^bg#(?:[0-9a-fA-F]{3}|[0-9a-fA-F]{6})$/;
+// Matches (fg|bg)?#RGB, (fg|bg)?#RRGGBB
+const hexColorRegExp = /^(bg|fg)?#([0-9a-fA-F]{3}(?:[0-9a-fA-F]{3})?)$/;
 
 /**
  * Parses a hex color string into RGB components.