Purple ==> A secret my muse would not want yours to learn.
Billy didn't trust Kate at all when they first met. He was convinced she was going to rat them out to the authorities, out them as superheroes (and him as a mutant).
After a while, when he realized that Kate was pretty much his best friend, he felt guilty for ever thinking she could be capable of that.
Mauve ==> What my muse would like to tell yours, but is too embarrassed/scared to say.
Billy is always trying to ask Kate to play her cello for him, but he can never pluck up the nerve.
Black ==> How my muse would go about killing your muse (assuming my muse were given cause.)
The strange thing is, compared to the rest of their teammates, Kate should be the easiest for him to best... but she's actually the hardest. She's seen him fight and knows his strengths and weaknesses, so she would definitely give him a run for his money. He'd end up cornering her, relieving her of her weapons, and then, most likely, simply stopping her heart.