In Dragon Ball, when a fighter changes his ki color usually means a transformation. The only exception I remember for this are Vegeta's different ki colors like the lilac ki color when he makes the Galick Ho attack, or the yellow color he gets at some point when he first fought Goku, or the light blue color he got a couple of times.
Does Kefura's red ki means something more or did she just get that color because she was performing a strange attack?