I am trying to think of a way to do the knife myself, and I am still trying to figure it all. All the ways I have thought of require time, and are complicated since I actually want to make mine light up.
As for her leotard, Royal blue would be the best way to go, and as for her hair I would go with the basic violet purple, like the shade a purple crayon would come in.
2012 Convention Plans
Dragon*Con: Tinkerbell (Peter Pan), Cordelia Chase (Angel), Jessica Moore (Supernatural), Red Playboy Bunny, Belle (OuaT), Crystalia Amaquelin Maximoff (The Inhumans), Abigail Brand (X-Men)
NYCC: Kitana (Mortal Kombat 9), Scarlett (GI Jo), TBA
Super Mega Fest: Princess Python (Serpant Society), TBA