It might be nice to get confirmation on this one.

I spent a lot of time (perhaps too much, haha) searching the guide, looking at probably every moth page, and I can't find anything else that could possibly be a match. The color is off, but the wing shape and pattern is perfect for this species. If you look at my moth's forewings you can see a faint yellow "spot" in the middle, which corresponds to a more bold yellow spot in the other specimens. The scalloped pattern at the edge of the hindwing is a match too, and there is a trace of a wavy white line at the edge of the forewings as well (like on the lighter specimens). From what I've been able to gather, only T. californiata and T. haesitata occur in California, and the latter has heavily-patterned hindwings.

I'm going to bring this moth (and many other insects) to the California Academy of Sciences soon to hopefully identify them to the species level... Until then, I can't think of any other possibilities for this moth.