hergin
2
What you mean is a repeating group inside a repeating group. Outer repeating group is color and inner one is size. That’s how you can display the thing you showed in your second picture. However, my question would be “why” in this case?
Because you can do the thing in your first picture in two repeating groups on top of each other (at the same level). A repeating group for color and another repeating group just below that for size.
Simply, what are you trying to achieve here?