If you go in early October, you'll still get pretty spectacular colors (see Photos below, taken end of first week in October).
Weather is cool...good to great for hiking, essentially no bugs other than the occasional fly, moderate day hiker foot traffic.
Sam is right that on some weekends, in the state parks, the trail may be temporarily closed because of hunting permitted during deer season.
As the month progresses, it will be noticeably cooler. Night time lows in the teens for late October or 20s for early to mid are typical.