Neutral format (sometimes called open) are mainly STEP and IGES files, sometimes Parasolid. Such files are mainly used to transfer 3D geometry. But in the file you can save, among others:. appearances (texture).

The format works great for SOLIDWORKS parasolid (for SW native), which allows the transfer of appearances both in parts and assembly.

In the case of STEP (both0 203 i 214), despite the option to save appearances being selected, I couldn't save them to a file. But interestingly, I often receive STEPs and these appearances are saved there. So it looks like this, that other programs handle it better.

Remember one important thing. In an open import file in SOLIDWORKS, most often, appearances are assigned at the operation level (IMPORT) and not at the level of the object or the entire part.

Therefore their deletion/replacement must take place taking into account the hierarchy.