warmanw Hmmm, I am actually not sure if this is a bug or not. The condition for enabling attachment color changes even in animate mode is to select multiple attachments of different types, but I think this is allowed considering the possibility that the selected attachments may include attachments such as clipping, bounding box, path attachments, etc. whose colors are not actually related to the animation.
It would be possible to disable attachment color changes when the current selection includes region or mesh attachments, but I personally think it would be better to leave the current behavior as it is, as I think it would add more work in some cases.
(I would have thought that if changing the attachment color was only possible when certain steps were taken, then it should be fixed as a bug, but as far as I have tested, the behavior seems to be consistent, as you can always change the color when selecting different types of attachments at the same time, regardless of what the previous or subsequent operation was.)
