Is it legal to alter a California license plate?

Over the past several weeks, On the Road has received letters from readers asking or commenting about our previous column discussing California license plates. We received emailed images of darkly colored plates, license plates with brightly colored lettering in red or other colors, and the like. Readers reported that they often see colored or modified license plates on vehicles, on what appears to be legitimate license plates with valid registration stickers. A few readers said they thought these were illegal, but were unsure.