Balls do not have the genetic pathway for erythrin synthesis so we will never see actual red in them. The “red” that so many people try to point out comes from the interaction of xanthin and melanin pigments interacting to create an umber unertone.
The closest we will get to red is by deepening the yellows into the orange range. Best morphs for that are combinations involving OD, YB complex, Enchi, and a couple other “saturation”/"concentration-type mutations.