2. it's disabled text. Earlier, this color was dim and dark, now it's light dim and light (it's for dark skins). how do you think disabled text must look? some mockup?
See the difference between the two 'disabled' lines in the skin, and the 'disabled' elements in the plugin:
But as I said, it could be because the skin is using the 'contrastboost' element to improve on the contrast of these elements.
Just as a general comment on the concept of 'disabled':
I think there are (should be) two versions of it.
1. for elements/functions that are currently disabled, but you may want to enable. So you will need to be able to read that text.
2. for elements that are currently not functioning, but also provide no useful information. Such as 'back' and 'forward' arrows in navigation panels.
These arrows (such functions) may be completely invisible when they can not be pressed.
But this is more of a general observation.
While I think there are a few locations in MusicBee where this distinction could have been useful, I think you can ignore the consideration for your plugin, since probably every disabled text or button will provide some useful information.