You always have to watch your liquids with M&P - if you add too much, your soap won't solidify. The rule of thumb is 1Tbsp per pound of soap. You can also use liquids from cooking vegetables - beets, asparagus etc and reduce until it's really concentrate. That way, you only need a little bit. You can also use spices: cardamom, paprika, mustard etc. Add a little bit to a small amount of melted base, stir well and then add to the rest of your melted base (otherwise, you end up with clumps - same goes for clays, which, BTW, make nice colours too!)