Is it decided on the day whether to wear kumadori?

Kumadori is not added or dropped according to the day's mood, because it is part of the kata that makes a character's nature visible. Once the play and the role are fixed, which kuma is taken is all but fixed with them: red suji-guma for the aragoto hero, indigo for the court villain, brownish tones for demons and monsters — a system of correspondences. Change it arbitrarily and the audience misreads the figure.

What, then, does the actor judge each morning at the mirror? The handling of the brush. The same suji-guma reads differently against a different complexion; if tiredness shows, the lines may go in a little stronger. The size of the house matters: a large theatre requires strokes broad and heavy enough to carry to the far seats, while a small playhouse needs less. The lighting design too changes how the red comes across.

The design, in other words, is fixed; the implementation varies. What the kata draws does not move, but how it is drawn under the day's conditions is left to the actor. This is the sort of thing meant when people say kabuki's kata are not rigid. Play the same role for thirty days and there are thirty small differences. It looks the same, and not one day is quite the same as another.