attempts explicit assignment of a given  GFX->setupGenericShaders(GFXDevice::###); on a per use case, in order to avoid using  .samplersDefined = true;  to trigger a fallback assignment,  where ### largely resolves to GSTexture
 (also attempted GSModColorTexture and GSAddColorTexture, with no noticeable difference.) It fails to do so.

Note that additionally, reverting PrimBuild::end() to  using:
   if ( useGenericShaders )
      GFX->setupGenericShaders( mNeedTexture ? GFXDevice::GSModColorTexture : GFXDevice::GSColor);
continues to make the difference between whether or not PrimBuild::color(tBlipColor); modulates the texture. (though I was able to to trigger color modulation when the textures were not being applied due to removing instances of  .samplersDefined = true)