One of the things I have in my Supergirl Returns series is that in her secret identity she admits that she looks a lot like Supergirl - but claims it's deliberate, because she's a fan! She doesn't try to change her hair colour or style, she just says that she always has her hair done in a Supergirl style, and has entered and won look-alike competitions etc. Her only disguises are contact lenses, which change the tint of her eyes from intense blue to blue-grey, and a change in posture, attitude, and speech.
