Riding at night with no lights is just dumb. The helmet color doesn't really matter as long as the bike has the legal + requirement of active lights.
Additional reflective gear is even better, but nothing replaces redundant, active lights. I have two predominately black helmets and a predominately light blue helmet with 3 colors of reflective tape stuck all over it. I have actually started back wearing a helmet, now that I have started playing around with a helmet mounted light to augment my handlebar mounted headlight. The spare 'bar mounted light that I've been carrying in my repair kit still goes, since I consider the 'bar mounted headlight the primary.
On bright, moonlit nights I do ride on the highway with my headlight(s) off, but this is only when (often, the majority of each morning commute) there are no cars visible in either direction. This is nice, since there are no streetlights, nor any other ambient light sources, for about a four mile stretch of my usual route.
(It's rare to see another cyclist on this route during daylight. I have never seen another cyclist on this route at night, same for pedestrians.)
Riding at night with no lights in a populated area shows a single digit IQ with no regard for self or others.
Except in the case of law enforcement. I have a friend on the Sheriff's Dept., Bicycle Squad, who tells me about being able to ride right up on folks at night, completely unnoticed.
Reminds me of the old TV show, "Who knows what evil lurks in the hearts of men?
The Shadow knows."