“Thursday, attorneys representing artist Kent Twitchell filed a claim against the U.S. Department of Labor in connection with Twitchell’s large-scale mural “Ed Ruscha Monument” — a six-story portrait of fellow artist Ruscha on a building owned by the federal agency — being painted over in early June. Twitchell said he received no notice, as required by law, that the paint-over would take place.Within the past few days, two more downtown murals, Frank Romero’s “Going to the Olympics” and Willie Herrón’s “Luchas del Mundo” (Struggles of the World) were partly covered with mud-colored paint, an apparent error by a Caltrans work crew cleaning up graffiti.”