That would be an interesting poll, I feel a lot took the other side of it. His dark costume suited the story and tone, and it was jarring (and felt forced) when he was in the suit, That's my 2 cents.
I think having a guy actually being purple colored, would feel "Batman & Robin" ish. Maybe letting us see that's his "real appearance" and he warps everyone else's perception, or something like that could work. But seeing him purple for any extended period of time would be pretty far from the vibe the show has shown so far in the teasers/trailers.
I'm not very familiar with the character from the comics, but if he really is physically purple in the comics, I think they could do it justice by simply having Killgrave be heavily laden with purple motifs. Have him wear purple, have his "powers" seem to invoke a purple aura in people, etc.