If she's grey don't use.  Rather go to Sally's Beauty supply and get Miss Clairol, pick one of the shades in the GREY BUSTERS (same level and tone of mom's hair if she just wants to match her natural color--no more than 2 shades lighter than her natural level and tone if she wants to lighten her hair slightly), grab some 20 vol. and process 45 mins.  Don't trust that boxed stuff.  Those pics are just too inaccurate. 

By the way what level and tone is mom's hair?

I see on the box of Natural Instincts it says "Now with improved gray blending for rich, dimensional color" which would lead me to believe it's ok for gray hair. It also says not to use on hair that's more than 50% gray, which would mean less than 50% is ok. And it gives a recommendation of what else to use if the hair is more than 50% gray ...

Rebekah -- If this Natural Instincts has peroxide (low, it says), then how can it be considered a NON-permanent dye? Also, what does the "ammonia" in hair color do? I see some say "no ammonia" -- does it just dry out the hair or alter the color? I could probably try to figure this out on my own but since you know, I'm sure, I'll just see what you have to say.  Thanks.

I'd follow Rebekah's advise and use Clairol Grey Busters. It's a great product and contains extra neutral pigments that cover grey beautifully.

As for Clairol Herbal Essence, they've reformulated it to be a permanent, no-ammonia dye. (Revlon Colorsilk is also a no-ammonia permanent dye.) These dyes, while gentler on the hair than regular ammonia containing permanent dyes, tend to fade quickly and aren't very good quality. There are professional lines of non-ammonia permanent dyes which are fantastic and can even lift several levels, but unfortunately, you'll have to go to a salon to get them.

Ammonia is a chemical that opens the hair shaft allowing the hair to "grab" the color. Problem is, ammonia also damages the hair proteins, leading to weakened hair or even breakage if the dye is used improperly. That's why it's very important never to reprocess your entire head of hair with permanent dye on touch ups. 

Natural Instincts is a semi-permanent dye. Semi permanent dyes do not contain ammonia. That's why they are marketed as gentler on  your hair than permanent dyes. However, the color will fade over time. Also, the processing solution (developer) does contain a small amount of peroxide which can slightly lighten your natural hair color. You won't notice this until the semi-permanent dye fades. Please note that these dyes are deposit only; therefore, you can't lighten your natural hair color. They are great dyes to match or tone your natural hair color. While I've heard and seen good results from Natural Instincts, I think there are better semi-permanent dyes at Sally's. Try Clairol Professional Radiance Colorgloss, a super high gloss semi-permanent dye. It's great, gentle and the processing solution contains even less peroxide than Natural Instincts.

Hope this helps.

I used Clairol Herbal Essences for a couple of years (in a variety of blonde shades). I LOVED IT! My hair never felt damaged. It was only after I started trying other OTC brands that I felt a little 'dry'. Of course, that was before I SWORE off doing it myself and only letting professionals touch my hair.

I don't have any grey, though.

The allergy test is important, even if you've been dyeing your hair for a long time-- you can develop allergies, even if you never had them before.  That's what happened to me-- I've developed an allergy to peroxide, so there are few hair dyes I can use anymore, and I have to read the ingredients carefully to make sure it's not in there before I buy one.  If I use hair dyes with peroxide now, my whole scalp breaks out in an itchy rash, and if I use peroxide on a wound, it gets worse rather than better :-( .

Natural dyes like veggie dyes seem to be all right, and some of the ones that wash out in like 24 shampoos or whatever.  It's sad, 'cause I like to make drastic hair changes, but haven't been able to :-( .

I've been tempted to see whether highlighting would be okay, since they don't actually touch the scalp, but I'm not sure if that's a good idea or not.