All excellent suggestions. Camel's Hump and Breakneck Ridge are favorites, and climbing in both the Gunks and the Adirondacks is first-rate.
Here are my 2 cents:
The town of Hudson sits on the east side of the river, just across from the Windham-Blackhead Range, which forms the northern escarpment of the Catskills. If you can carve out a total of 4-5 hours, I suggest a clockwise loop of Blackhead, which is a 5.4-mile lollipop with about 2,000' of total elevation gain. It's only a 40-minute drive or so from downtown Hudson to the trailhead at the end of Big Hollow Road.
Here's a SummitPost link with directions, which are right on the mark:
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Here are tracks for the loop, done clockwise in winter after heavy snowfall:
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There are five junctions on this loop—left at the first; right at the second, third and fourth; then left back at the first/last junction to return to your vehicle.
Here's a map, although there are better ones out there, like from the NYNJTC.
Here's a photo, taken 9/21/09, of Blackhead's neighbor, Black Dome, as seen from the trail along the western slope of Blackhead:
It's a far cry from Colorado, but it's still nice. The colors should really be popping the first weekend of October. If you choose this loop, take a left at the first junction onto the Batavia Kill Trail and do it clockwise. You'll see a lean-to on your left, and then you'll do a fairly steep ascent of Blackhead; the final 0.9-mile stretch to the summit features about 1,300' elevation gain. The summit is bearded, but shortly thereafter, as you descend the west slope, you'll get those views. Also, at the fourth junction, you'll be down in Lockwood Gap, which is cool because it's a perfect example of the often tight, narrow cols between Catskill hills. (Our euphemism for "small" is "intimate."
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Another decent option in this area would be to do a simple out-and-back of Windham High Peak on the Escarpment Trail. The large parking area sits along Rt. 23, which you'll pass if you go to Blackhead. Windham is 6.8 miles R/T with about 1,800' ele. There's also a lean-to on this route, as well as some decent views from near the summit, though you're looking north at the flatlands south of Albany.
The only other option I would recommend, based on your time constraints, is checking out Kaaterskill Falls. The town of Hudson sits near Exit 21 on the New York State Thruway, so you'd want to get on the Thruway, drive south about 10 miles to Exit 20, then head west on Rt. 23A for about 12 miles into Kaaterskill Clove. The road winds sharply through the notch, and at the hairpin turn you'll see the trailhead on your right (north). Keep driving up the hill and park at the pullout on your left, then walk back down the hill a quarter-mile to the trailhead. The trail up to the base of the falls is just under a half-mile with about 450' ele. Watch your step here, though, both on the road and near the falls.
Best of luck. I hope you (and the wedding couple) have great weather.