First, you modify the textures of, for example, the Mustang Fastback. The textures names are vpbullet_*color*, for example, vpbullet_red. You modify the texture in Photoshop or another software and save with same basename but different color, like vpbullet_black and convert it back to .tex.
Now you open in Zmodeler the Fastback .pkg and go to export. a windows will open, called "Exporting properties". You got to make sure that the "Type of exporting" is set to "Standart vehicle". In the "Textures" section, click "Multiple colors (paintjobs)", select the color that is already there (probably "_blue" ) and remove it clicking on "remove". Then you just gotta go to the textures folder, and get all the colors that belong to that car (vpbullet_red, vpbullet_green, vpbullet_black<--yours, and the others that start witht he car basename) and then you gotta in Zmodeler write in "Replace suffix" the first color, like _red and in "with suffix" _green and click "Add to List", and then Replace suffix _red with suffix _black until all colors are there. Then you just gotta click "Export", zip it, and be happy
P.S.- When Replacing suffixes, the colors must be in the same order as in the car information file, so if there is Red|Green|Blue|Black, you gotta do it by order, first replace _red with _green, then with _blue and finally with _black
Hope this was clear
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