Hi there Blue,
Well, I'm new to colorants too! Today I tried cocoa powder with my un-natural scents of chocolate drizzle & coconut breeze (WSP), a 2 layer bar, I just unmolded it, the cocoa color is way lighter than I expected. Still, a rather pretty bar . . .
I took my 1 lb CP recipe (I use 1 lb for experiments), took a bit, probably about a TSP of the oils out, mixed those with the cocoa powder, sorry, no exact measurements, I'm a fly by the handle type, mixed in cocoa until it was still liquid, not a paste, added it to half of my batter, I knew it wasn't as dark as I wanted it then, but wow, after the soap gelled, it's way light.
So if using cocoa, I would suggest using a lot more than I did. I just mixed up my lye, I will try another batch tomorrow, I will try 2 TSP oil w/lots of cocoa.
For un-natural colors I just bought the 8 from Select Shades, but have not tried them yet, am dying to! but have a rather large order to fullfill before I have time to play . . . aw shucks!