As long as that text_de is in your steamapps directory (bottom screenshot), every language but German will update properly.
Looking at those dates in the screenshots you posted: [Tool] Rainbow Filter (Item Highlighting) - #730 by Xeaker
steamapps folder (bottom) text_de was created first, then you added the path setting in the program (my reply screenshot) which will write files into the middle screenshot instead, so you created text_en and couple weeks later you made a change to German and wanted to update it, but the files were written in the middle screenshot, creating the new text_de, rather than replacing those in the bottom one.
Changing colors works fine for me
