Question about gray

My boyfriend and I got a gray rescue mare supposedly about 15 yrs old. We were told she is a qh/tb mix but I have my doubts. She was in very sad shape but is slowly coming back after lots of tlc. She has red flea bites so I assumed she was a chestnut, but I just washed her tail and found a few black hairs. Is that an indication that she started out as a bay? It really makes no difference
To us what breed or color she started out, she is a complete doll and won't ever be bred, I'm just curious:). Thanks!

Possibly. Does she have any black flea bites on her lower legs? There's a gray TB gelding at my barn that I thought was originally chestnut until I looked closer at his legs, which have dark flea bites.

Weird! I never thought about that! That's really cool.

Side note: Lacey has mostly black fleabites (neck, face, chest, legs...) with brown ones intermixed with black on her shoulders and 100% brown ones in her flank areas... I always just figured she started out black because her dad was black but....?
Sorry, OT.

Lacey may have been brown if she has brown fleabites around her flank.

The grey Arab at my barn was definitely black but he has the weirdest markings I've ever seen on a gray: he has cornmarks... I asked his owner about them and she said every spot he has was once a bite or something and grew back black instead of gray, similarly to the way a bite mark grows back solid on a roan. Very, very odd.

That is really weird! Are the black marks graying? Or are they staying the same shade?
Grays, gotta love them!

That's weird about Lacey! But possible. Her dad was a 1970's model so I guess he definitely could have been super dark brown and mistaken for a fading black... Or there's always Lacey's mom, but who knows anything about that lady.
All I really know is that Lacey started out dark enough to look "like she had been covered in lace and spray painted black" (that's what her previous owners told me about how she got her name... )....
Brown could definitely be a possibility.

There don't really seem to be flea bites at all on her legs, pretty much just on her neck and sides

As far as black in the tail, we had a darker chestnut colt that went grey. When he did, he went from a dark chestnut into a dark grey (getting dark grey and black looking hairs in his mane and tail). When he finally turned a very light grey, he had a few flea bites scattered on his neck and body that were chestnut colored. Grey is a weird and unpredictable gene that can really change up a coat color in the processes instead of just covering the base coat.

As SunnyDraco said, grey can do all sorts of weird things lol. Most of the time, it does tend to make the horse get a lot darker before they get lighter lol.

Pics? =D