Meh. I was expecting a lot more fiery red and orange but so far Theodore Roosevelt Island is still mostly green; just some yellow around the edges, with just a few trees here and there going bright red. The marsh area has a lot more color to it, but I think it’ll be another weekend or two before you get the kind of Fall color that makes local news.
You can get to Theodore Roosevelt Island with Metro and a brief walk. Just get off at Rosslyn, walk over to Key Bridge, turn right on the trail just before the bridge, and walk till you see a parking lot and footbridge. It’s nice. Try it if you haven’t yet. The earlier you can go in the morning, the greater the chance of seeing some wildlife. As it is, we did see a snake.