When fans picked the blonde version of female Commander Shepard to appear in the ads and videos for Mass Effect 3, they weren't voting for a hair color; they were voting for a hair style. Now we're voting for the hair color.
I wasn't a particularly big fan of the blonde Shepard recently voted in as the official FemShep of Mass Effect 3, but I really did dig her hair. So did a lot of folks. BioWare knows this to be the case, and has opened up round two of the voting to let fans determine which color that lovely hairstyle should be.