When closing a WP Theme project and opening another one without exiting Pinegrow the theme export of the secondly opened project can be corrupt.
In my case:
I openeded a classic theme project and made some minor changes in a query loop. Exported the theme.
Then i do “File / Close Project” and open another Project which is a hybrid theme where i had no colors in the design panel but just fonts. After opening this hybrid theme project i can see the colors of the other project in the design panel. Exporting the theme breaks the block editor color pallette coming from the ACSS Plugin. Just having the default Gutenberg colors in the blocks color selector.
I quit Pinegrow completely and reopen it. Then loading the hybrid theme project. The Design panel is how it should be. No colors defined. I do “WordPress / Clear the theme folder”. Then a new “WordPress / Export the theme”.
After that the color palette from ACSS is working again.