How to identify a given string is hex color format

Question

I\'m looking for a regular expression to validate hex colors in ASP.NET C# and
am also looking code for validation on server side.

For instance: #CCCCCC

Answer 1

all answers mentioned RGB format, here is regex for ARGB format:

^#[0-9a-fA-F]{8}$|#[0-9a-fA-F]{6}$|#[0-9a-fA-F]{4}$|#[0-9a-fA-F]{3}$