California Photographer posted the following fall color report for Napa Valley on 10/31/12
With most fruit in the tank, harvest is winding down, and the colors are revving up. Still quite a bit of green across the valley (especially the young vines), but many vineyard tracts turning to soft yellow and some gold. Interestingly, some of the leaves turning straight from green to brown. A few spots of deep red, but no widespread intense color yet. Virtually no leaf drop yet either, so the vineyards are still full and lush. Lots of patchwork contrasts across the tracts, even by the row within tracts (different varietals turning color at a different pace). The surrounding landscape trees are well ahead of the vines in terms of developing color. Traveling Silverado Trail southbound (Calistoga to Napa) in the late afternoon offers many lovely photo opps.
Read older fall color posts at California Photographer