The color used to display an object is specified in one of three ways. If ColorSource is ON::color_from_layer, then the object's layer ON_Layer::Color() is used. If ColorSource is ON::color_from_object, then value of m_color is used. If ColorSource is ON::color_from_material, then the diffuse color of the object's render material is used. See ON_3dmObjectAttributes::MaterialSource() to determine where to get the definition of the object's render material.