Originally Posted by Tycho

Most graphic editors have field for the colors in hex values. If not, the net is full of such converters.

The words in .exe are reversed, you need to read backwards.
So, if your color is RGBA: 1F45B4FF
In .exe it must be ABGR: FF B4 45 1F
Be careful to not revers a byte value itself, B4 must stay B4 not 4B.