It's possible your characters may have Mass Markings. I suggest redownloading the markings and see if that fixes your problem. www.tinyurl.com/aug22massmarkings
Hmm, I am not sure if the floof is talking about these markings (those are extra), it's about the presets that they have made or a file is miss placed. Remember that if a marking is missing from the texture folder your characters will not become white, they just wont appear. I don't usually find my presets in the 'textures' folder, they should be in the 'presets' folder. :3 When you make preset they have: eyes, body, tail, face and both wings and mane are optional. When you go to preset make and click 'preset_number' you see them right? So make sure to export it to get your '.fhp' file.

Then finally, you place that file in your presets folder.
If you put, for example what you did, more than 1 preset in your texture folder, your character will most certainly become white. Same thing if you do to any 'preset_number' folder, if you add more than 1 preset inside with the eyes, body, etc. files, your character will become white so this is not a glitch.

I hope I helped, and tell me how things work out. :3