Turquoise.
Why? Well, my mother painted our entire house interior (not the exterior, in our small Canadian town the neighbors would have gossiped about us) in this color in 1955, excepting only my bedroom, as I threatened to leave home if she did. I was an only child at the time, so I got my way.
Years later we ended up in New Mexico, where I dipped deeply into the native culture and learned to love the color for its unique cultural meaning.
Dark colors in the darkroom deaden everything, including one's soul. Framed prints in natural wood frames look good on a darker wall, however.
Just go to your local paint shop, gather a few samplers (the small brochures the paint companies put out to promote their latest colors), go home, mull it over a good whisky or two, and decide.
So what color is my darkroom? Huh... I don't know. My partner selected the color and did the painting, the room is also used as an architectural drafting area.
I do know it isn't turquoise. That's about it. One color is as good as another.