I'll plug the PNW. We don't have the deciduous forest of the NE, but we still have a lot of it; combined with aspens, larches, dogwoods and the vineyards. All which color at different times on some pretty backdrops.
We're also bonkers with the festivals, u-pick apples/pears/pumpkins. Halloweentown was filmed in St. Helens, OR and they convert the town back to Halloweentown for October. Like, full gas the entire town and they double down with Twilight shenanigans since it was also filmed there.
Just Google "fall" for Portland Japanese garden, Multnomah Falls, Columbia Historic Highway, Silver Falls State, Columbia River Gorge, Mt. Hood to get a flavor!
There's also some unique fall offerings. The alpine larch is native to only the Rockies and Cascades. We did Blue Lake in North Cascade with our 4 year old last year to catch the larches. Totally doable hike with kids if you're into outdoors stuff: