i don't necessarily go by the coloring because a lot of bettas look really dull and drab in the store compared to what they will bloom into when they are healthy and happy. the boy got one that was pale and whitish... she turned out to be a yellow gal. you just never know.
i have a female in my 10g community that is colored very similarly to Taffy, and she was pale, almost completely white, and suffering from ich when i bought her. she went from a mopey little sickling to a colorful beauty during her time in teh hospital tank, and now she is the queen of her tank... she isn't aggressive, but at feeding time she bosses around my cherry barb, white clouds, cories... even my big, pushy neon dwarf gourami. she definitely likes her personal space =)