For CP, you need to make sure the colors you use are stable in the high PH batter or it could morph into a grey or brown color. Many M&P colors don't work well in CP. You generally need more color for CP and if you use mica, it won't be shimmery in CP.
I don't do M&P but I suppose as to actually adding the color, its fairly similar to CP. With CP, you add the color then blend it in with your SB, with M&P it mixes in easier. Not sure if thats the info you are looking for or not.
When I have to do MP, I use WSP's color blocks. That way I can melt the color along with my base, it's easier for me.
As for the CP, Obsidian said what I'd say.
When buying colorants, make sure you read the reviews, they can be very helpful.