Since December 16th, 2021, when Melia was split into herself and Olive, Melia's Pirouette Forme colors have been lost, due to them being changed when Olive took over. Because Olive is no longer an alternate personality of Melia, she can no longer change Melia's colors.

In other words, the colors of Pirouette Forme Melia are tied to her former alternate personality.
(This is the other way around for Olive, as the colors for her Aria Forme are tied to Melia.)

Yeah, I know. It's confusing.