After you cross the Golden Gate Bridge heading out of San Francisco, you end up in Marin County and pass through the Waldo Tunnel where the arch is painted like a rainbow (long predating the gay rights movement's acquiring the rainbow as the gay standard; the Waldo Tunnel rainbow scheme is supposed to be indicative of the rainy/sunshine climate that produces the rainbows that Marin -- and San Francisco, for that matter -- is famous for).
Here's a pic of the rainbow painted on the Waldo Tunnel:
The old joke is "That's the last color you're going to see in Marin County.", acknowledging that Marin County is practically 100% white, rich, and liberal.
George Lucas' notion to put up a public works projects on his land has got to have the Marin County Board of Supervisors bouncing off the walls trying to come up with a way to kerbosh his idea without appearing racist.