Red Koi hm
Koi pattern, falls under marble genetic. Usually Koi is Red, yellow or black patches. Even the latest type of trend, candy nemo falls under marble gene. Their base colour is cellophane, then red/orange/yellow/black that covers on top which showcase the koi like pattern.
Usually in a whole batch of koi spawn, not all will turn out really pretty koi pattern. In the video shows one with alot more red marbling and another one with lesser red marbling, some got even lesser or some could be more too. That's why in a whole batch, at least half of them will not turn out really desirable.