Cotton (the white haired one) gives the entire squad 2x skill proc the turn after anyone is hit, 1x damage negation, 20% skill drain up to 50% max HP per skill proc, +50% defense, 2x guaranteed chance to survive a fatal hit and +40% crit damage. She also grants one Attack-based ally up to +200% crit damage in chunks of 50%, with each chunk activating after the ally has dealt a critical hit five times.
I don't remember who the other rainbow is, but I'm betting someone else does.