Sketchbook: Painting of a Robin Redbreast

I used to love seeing the fat little robin redbreasts in England. When I was growing up it was considered good luck to see a Robin at the first of the season.Do you know HOW they got such bright red chests?
According to an Old English folk tale "when Jesus was dying on the cross, the Robin, then simply brown in colour, flew to his side and sang into his ear in order to comfort him in pain.