Well.......
When Purple Kiss debuted, Goeun [ the girl who was usually in the center ] wore that hair color for their debut song Ponzoña.
They've also worn purple outfits for the MV.
Personally, and maybe internally, I thought it'd be awesome if they had alternated who would have the purple hair color in upcoming comebacks, but sadly, that never happened.
Also, as someone mentioned before, their latest comeback Sweet Juice MV had purple outfits.
Ironically, PIXY wore a splash of purple for their comeback MV Addicted in the 1:07 mark. I say splash because the outfits had dark blue combination.
But, yes, more purple if possible by other groups.... which means they're "admitting" to PK of being subconsciously influenced into wearing the color in some way.
Edit ~ And since PK debuted, purple became my new, personal favorite color.