It's a little light for a seal brown, but close enough that we'd accept the mane color. Our only concern is the paint like marking, which is a lot of white for a horse not carrying a paint gene. The markings most closely represent an overo from what I can see, so adding nO to the genotype would fix that.
TLDR; color is fine for a TB, that large of a white body marking would probably need a paint gene. Overo gene is suggested!