A reddish-brown stain.

He had reddish-brown hair, plaid shirt.

His hair is reddish brown. Reddish brown and a white beard.

It is a reddish-brown substance consistent with blood.

Do you see why I will only commit to a reddish-brown stain?

When you magnify the rash, it looks like little stringy white things coming down in a reddish, viscous fluid with brown, lumpy things growing inside... you know, spaghetti and meatballs.