shut down gmod then try deleting the following folders
C:\Program Files (x86)\Steam\steamapps\common\GarrysMod\garrysmod\cache
C:\Program Files (x86)\Steam\steamapps\common\GarrysMod\garrysmod\download
C:\Program Files (x86)\Steam\steamapps\common\GarrysMod\garrysmod\downloadlists
C:\Program Files (x86)\Steam\steamapps\common\GarrysMod\garrysmod\downloads
sometimes addons can persist in your cache

check your addon subscriptions, there are multiple PPM versions.
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=1139652726 is PPM2 the only thing on that list that you are subscribed to?

i can not even open ppm2 and my pony is error in colors. why so?

and the pony wings stopped working...

well this ppm2 thing is still a little new they might still be working on it

Sorry to jump in late here, but Im having a similar problems, but it doesnt fully break for me. When it breaks for me the wings fail to change when you try to go batpony. The buttons to select the different areas of customization dont appear until you hit the advanced button, but them the background stuff fails to load and some of the options you have already picked will disappear or will not be a option.These problems only seem to appears when you use the pegasus, Allicorn, and the batpony versions of the two. Most problems seem to revolve around the wings and the coding for the buttons itself.