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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- Uniform (Little Witch Academia): 18% (Sewing) Summer 2017
- Paladin Armor Shiro (Voltron: Legendary Defender): 8% (Patterning) NOVACon 2017
- IPRE Robes (The Adventure Zone): 19% (Patterning) Summer 2017
- Leo (FE: Fates) : ??% (Wig Styling) ????