From my experience with natural colors this is what I can come up with at the moment. I have only done CP soaps, I add most at light trace with my EO blend.
Black Walnut Hull Powder: a nice tan to dark brown depending on amount -- love it, fades some in sunlight.
Cocoa: A nice tan to dark brown depending on the amount -- I like the look of it, but it bleeds a lot if you put much in.
Activated Charcoal: Deep rich black -- a little goes a long way! Bleeds a little in the water.
Safflower Powder: Yellow to orange/peach color with nice little specs -- fades a bit in the sun.
Dandelion Leaf: Dark green with slight brown colors -- fades to brown and loses most it's green in the sun.
Burdock Leaf: Same results as Dandelion leaf, just slightly darker.
Red Sandlewood Powder: Peachy Orange i'd call it, and fades some in the light.
Paprikia: Yellow to peachy orange color depending on amount -- This one seems to hold it's color really well from my experience.
Turmeric: Yellow/tanish -- I like to blend this in with browns and tans, it livens the color some. Fades in the sun a bit.
Indigo: Grayish blue -- holds its color decently in the sun.
Annato Seed: Infused olive oil 24 hours before use -- deep orange color that holds up well.
taken from:
http://www.soapmakingforum.com/showthread.php?t=50630