What is it when most toenails on one foot are like a dark color and not dark colors on the other foot? there is no pain or anything. they turn dark.

Onychomycosis?: If the involved tonails also are thickened and rough, probably it is onychomycosis, a fungal infection. It's usually harmless, but sometimes can lead to secondary bacterial infections; and as you have seen, it's unsightly. Treatment is available but expensive -- in the US, not covered by many health insurance policies. See your doctor for diagnosis and advice.