Why is there a leading “#FF” in hexadecimal color values?

Question

I\'m using Expression Blend 3 and am writing some of the XAML by hand, specifically the color values of controls.

I have a list of RGB colors already converted to hex

Answer 1

The 'extra' FF is an alpha value (degree of transparency). If you only have three hexadecimal pairs, the alpha value is assumed to be ff (no transparency). However, if you compare #335A7F39 and #FF5A7F39, you should see a difference.