Sebastian had a black winter coat. It isn't yet summer and he already looks pretty "rusty". Is he a bay or black horse? I love him either way and wouldn't spend much money to have him black, BUT I read that a Tablespoon of paprika morning and night will do the trick. Has anyone ever done this?
I read somewhere that if a horse is feeding from "red" earth (and yes, NC has red dirt) then it is likely full of iron which competes with copper metabolically. Copper is very important in maintaining coat color. He is pasture boarded with a nice shed to use to get out if the wind, rain... and sun. His pasture does not have much shade, if any.
His father is a black Friesian, his mother I would say, a Bay Paint.
...and below is a photo of him last October when his winter coat was starting to come in: