I agree with Ichigo-- those characters have two totally different colours, and unless you dye the wig, I don't think one is going to work for both.
Going to con with only one cosplay can actually be a lot of fun, though! If you're really not up for that, though, you could always pick a cosplay that would make use of your natural hair.
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- Pearl (Steven Universe): 34% (Sewing) Winter/Spring 2016
- Labelle (Animal Crossing New Leaf): 96% (Final Details) Katsucon 2016
- Pyrrha Nikos (RWBY): 56% (Weapon Work) Katsucon 2016
- Pyrrha Nikos Weapons (RWBY): 50% (Carving Sword) Katsucon 2015