Hi, can you please check if the corresponding material has "use_double_colormap_with_mask_texture" flag set in the "Material Shader Flags" pane in Material Editor. If this flag is set, shader requires a suitable mask texture in Diffuse2 slot to determine which regions of mesh will be affected by factor color. If you want factor color to be applied to the whole mesh, then you can unset this flag and no mask texture will be required.