Pray for clouds and rain!
October in the UP, you hope desperately for dead-calm and bright overcast with occasional rain to saturate the leaves. Bright sun is lethal because of the absurd contrast range in the forest. There are too many gorgeous waterfalls and neon forests to list them all, but you don't want to miss the white birch forest along the Lake Superior shore late in the season, because it reaches peak color later due to the moderating effect of the lake on temperatures. Wagner falls, Au Train falls, Sable falls,.... lots of 'em.
If you're stuck with sunshine, go for Grand Sable Dunes, which are spectacular in raking light. And if you have a whole month to spend, it's worth figuring out sunrise/sunset times and directions for scouted locations. If memory serves, however, most of the waterfalls are oriented north/south, so you'll still be praying for cloudy/calm weather.