Grays can be born any color I believe (solid or pattern), and as they shed out each year they grow lighter! I was really excited / suprised when I saw Sasha's color when she was born, then my trainer/instructor/friend told me she would turn gray!
Also, I believe to be classified as a gray, the horse has black skin and white hair. (They may have pink skin where there was white on them when they were born) Like Sasha's little white star has pink skin and the white on her back left foot, but the rest of her skin is black.
Sasha -few weeks old (her dad was a dark brown / white paint) (her mom is a flea-bitten gray *seen in picture) Picture 268.jpg
Sasha -2 yrs old. Mom's Camera 091.jpg
Sasha - 3 yrs old -- taken day before yesterday
-her neck looks a little funny because of my angle and the way she was bending trying to nibble on the snap of the lead rope.
You can see how she's lost pretty much all of the red out of her coat color. Also, you can see how white her face has turned. Image04152011161407.jpg
She will eventually look like her mom Dandy (My avatar).