I'm not sure if I understand that. I have copied several each of my saved skins for the XFG, XRG and FBM into the "skins" folder under the lfs folder. If I click on the "Colours" button under the FBM car settings, and then the "Skin File Name" button, I see the box stock skins for the FBM along with the ones that downloaded for my last installation of LFS.
If I try the same thing with the XFG or XRG, when I click on the "Colours" button I get the "Can't Change [default] - Select Personal Colours" message. The same thing happens when I touch any of the colour slider bars, or click on the "Skin File Name" button. So I can't change anything because no matter what I touch (just for the XFG and XRG) I get the error message. So I cannot create a new skin/colour because the message always blocks me.