Painting red objects can be a challenge. I try to create a convincing sense of light in my paintings by pushing the warm/cool relationships in the subject. However, when you lighten red it often turns a cool pink (too much white) or it turns orange (too much yellow). The solution I've found is to darken the darks with blue/purple and lighten the lights with yellow/orange. This may be too much info! Anyway, the key is to push carefully in both directions.