I’d like to view the Swiss fall colors when they’re at their peak. I’ll be visiting between Zurich and Geneva for 5 days in October. What 5-day period in October would you recommend?
Also, my experience is that many of the trees on Swiss mountainsides are evergreen.
The fall colors usually aren't nearly as brilliant in Europe as in the US. You generally don't get the bright shades of red and yellow, mainly just brown. The color change-over usually coincides with the period when the atmosphere becomes much damper, so any color gets muted by a general pallate of grey. The peak also varies by weeks from year to year, so you're not likely to see it unless you stay for the entire month of October.
And as noted... most of the trees in the Alps are evergreen.
Actually I live in the Lauterbrunnen area and have lived here for 15 years and can say that the fall colors are spectacular. Towards the end of September and early October they are amazing with beautiful golden colors in the trees (not all are evergreens) and purple heather on the ground. There are also tons of wild blueberries to pick. Autumn is lovely out here and well worth a visit as it is usually very quiet. I would suggest visiting before the middle of October as a lot of things start to close down then.
Where there are larches you will see a beautiful soft gold when they turn color. It is a short window and hard to predict in advance, as the color change is driven by the combination of shorter days and colder nights, and varies with altitude.
I have always wanted to visit Oeschinensee (above Kandersteg) in early October to see the colors there: