I'd probably have to see mockup first, but I think I'd rather have a matching headstock.
If black was part of the whole trim, it could work, like on this ric:
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I could get down with black binding on the blue model for sure.
But to have everything white with a black head stock seems off to me.
I have a number of blue instruments, and they actually all have black headstocks (or part black in thr case of my guitar), but black is part of their trim. My Ric and my custom Jaguar are both blue with matching headstocks.
Model of guitar I have (also my preferred shade of blue):
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https://s-media-cache-ak0.pinimg.com/236x/b4/72/21/b472219e6c80ca171114977ec586df53.jpg
Ive also got the Casady bass I previously posted, which also has a black headstock, but has black as part of the trim.
Lastly, Ive got a TMB100 in an infinitely less sexy shade of blue with a black headstock with no black in the trim which looks out of place to me.
http://i121.photobucket.com/albums/o237/primussucks91268/Mobile Uploads/IMG_20150710_240633378_zpskxyjyy2c.jpg
So if were doing black headstocks, I think I'd like to see it with black binding, pg, hardware, TRC, and pickup. Unless a mockup changes my mind. I also think gold and red would go fantastic with this all black setup. Rootbeer should stay cream though.
Sorry, i know this is a heavy post, but I take my blue basses seriously.
Personally, I think the people who want these other colors should put there money where there mouth is. I don't mean that in a hostile way. Don't get me wrong, I'm all for manufacturers offering more colors (I won't consider a new Fender because I find their options uninspiring) I just know people like to fantasize about what should be avaialable, and never make moves when it becomes available.
You said you've got 8 deposits so far for these special editions, and adding these colors would make for at least 30 basses if your OEM requires a minimum of 5 (white tux, blue, rootbeer, gold, olive, and red, correct?) Not counting standard finishes. Colors can always be added down the road, but if people want them now, let them speak up with their wallets.