Ok so I choose, 100, 50, and 221. 100 divided by 16= 6 r4 =64 50 divided by 16= 3 r2 =32 221 divided by 16= 13 r13 =DD So I'll use the code #6432DD hope it works
If it were only 2 colors that go into the code you could make one but with the RGB setup it just looks like the rainbow. If you know the 3 colors and how they mix with each other then you have a pretty good guide in that.