Since bloodred seems to be a combination of a plainbelly trait which mostly follows the predictable ratios and selective breeding for high red, it's a bit confusing to work with. If you want to predict the occurance of the plainbelly trait, pick some other gene instead that neither parents have and substitute it for bloodred.
Just don't forget that you substituted it, and that the substitution will affect the outcome... you'll have to mentally convert things back to bloodred.