Don't worry, guys. Grey hair isn't the end of the world and you won't look hideous when it happens. : )
My older sister is 58 and doesn't have one grey hair. I started going grey in my late 40's and am now 60-70% grey I guess (I don't color it), my younger sister started going grey in her teens and is probably 80+% grey (tho it's hard to say since she has been coloring it all these years).
You just never know when it's gonna happen.