I recently did a 5 day mid winter trip in temps of about 5-15C (approx 40-60F?) without heated grips.
My gloves are mid weight.I had lightwight polypropylene liners which do make a difference.
If it was wet or early morning I also slipped on some plastic bags over the top.An old guy I somtimes ride with told me about this (sliced bread bags).They also make a difference.
I tried buying nylon overgloves from 3 bike shops without luck - have since tracked them down through a mail order co.
Dry gloves are important.
Next time I will probably get heated grips.
I dont know about the colour question - mine are black
Grant