So i cant really do anything to help with general issues related to colorblindness, i can help with this specific mechanic. He tethers to one end of the arena, powering up the color-coded attack. This will always be the cord in the center at the north or south(or do i remember wrong and its east/west?) of the room. The one on the opposite wall in the same spot that he DIDNT tether to will always be the opposite color. You'd have to disengage from melee range for the moment of the attack, but if it feels better then struggling to differentiate the colors then its worth considering.