Actually I believe it was closer to 2 years between the ages of 18 months and 3 years old that she did most of the greying that overtook the red, though even today the red base does come up often unexpectedly (such as the 2012-2013 winter coat).
Well, Dobe is my first experience with a gray horse and he had already grayed when I got him...though his shade has changed every year. I'm told that he was a buckskin when he was captured, but I'm beginning to wonder if he might have actually been a palomino and the darkening of the legs/mane/tail done by the gray gene made them list him as a buckskin. Maybe someday I'll have him tested.
This is the only decent picture I have of him as a 3 year old where his color is actually visible.
Here he was at age 4. Still dark, but starting to dapple instead of just the slatey steel gray color.
Here he is at age 7. He's right in the middle of the dapple stage and you can really see that his bloodmark on the side of his face is starting to stand out.
Here he is at 8, leaning less toward dapple and more toward white
And here he is last year, almost completely white at the age of 10.
Though he does seem to be getting more and more yellow fleabites as he gets older.
I haven't gotten any good pictures of him all slicked off this year because, well, he isn't slicked off yet. Funky weather has led to funky shedding patterns.
As for the melanoma thing, most gray horses will get them at some point in their lives. For some reason, they are most common around the genitalia and underneath the tail. Most of the time, they are nothing more than a nuisance or an aesthetic problem and cause no actual health issues.
Dobe developed his first at age 7 and developed another shortly after that. I had both surgically removed with no complications, but he has since begun to develop more at random places on his body. They don't cause him pain, but I plan to keep having them removed as there are a couple that are beginning to interfere with tack. The ones he gets are little hard lumps that just slowly grow over time. The first 2 that I had removed, one was the size of a shooter marble and the other was slightly smaller. The ones he's got now vary from the size of a BB to the size of a regular marble. I am currently tracking 5 that need removed; 2 on the side of his head, one on his back, and 2 on the top of his rump.
Smrobs, do the melanoma spots feel like little round marbles? If so, I think my little Envi has a few... There's one round, hard little lump on his back right below the end of his withers, which, if it is melanoma, will have to be removed. He has a couple other little ones but they're not in places that would bother him.
Now for a little color (or, more accurately, lack of color) update! Here's a pretty recent picture of him, maybe from last month- he was drying after a bath here so he's actually a bit lighter than this. Unfortunately what little dapples he had have been replaced with freckles... :( I'm not going to lie, I'm a bit jealous seeing all the pretty grey colors on here with nice dapples. Right now, he just looks mottled...