Parodied: A villain dyes her hair blond and undergoes an instant Heel-Face Turn. Her Mooks kidnap her and dye it bubble-gum pink. She reverts and kills them all for laying hands on her.
Zig Zagged: She reveals that she dyes her hair. Cue the Costume Test Montage as her younger self goes through a dozen hair styles and colors before settling on blonde. No one is really sure what her alignment is supposed to be now.
Averted: Hair color is not connected to morality; the good character can just as easily be a brunette or a redhead.