Anyone use this hair color? I don't want to change my hair color, I want to color grays. Since this doesn't have ammonia, does it not last longer than other permanet colors? I wouldn't say I have resistant grays or a lot of gray, so it should work for me, right? I usually use any old cheap hair color, but I got a coupon for this so I want to try it out. Is it a lot less damaging than other color? Thanks.