I would go with one (or more) of the BB sample packs. I have used the oxides and ultramarines one and they all perform great in CP soap. A little goes a long way (they are more potent than micas, start with 1/4 to 1/2 tsp per pound of soaping oils) and they really pop if you gel.
There is also a mica sample pack but I don't have personal experience with it. Anne Marie is great with her descriptions - if the color will mutate in CP soap, it's generally in the description.
The liquid lab colors are nice but not for swirls as they have a tendency to bleed or migrate.