Import noob question - messed up textures they turn full red

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Hi, I have a problem when I try to edit the textures on models, for example this building turns full red (or player corlor) when I change some texture of it, diffuse, normal, etc. and I don't know how to solve it. Btw, I'm using Quenching mod and in this example I put the textures in retail/buildings/undead/ziggurat but then are messed up.

Thanks