Here in Indiana, the North and North/East sloping hills are still the first place you want to look, but you can sometimes find it just about anywhere givent the correct conditions. One thing I haven't seen mentioned is oak trees. Ginseng as a rule, doesn't like to grow around oak trees. The leaves are too tough for it to come through in the Spring. Don't get me wrong, I have found ginseng with oak trees in the vicinity, but to actually be in an area where oak is the dominant tree, probably best to move on to more promising areas.
As for the plant yellowing, there are other types of vegitation that turns the same time as ginseng. The thing about ginseng, at least here, is that plants of a similar size normally don't get yellow right along side them. That's why when they're good and yellow, man they stick out like a sore thumb.
In Indiana, the season ended early this year. We were done maybe the third week of September. You could have found a little after that, but it what you would have found wouldn't have been worth the effort. In a normal year, I usually hang up my digger the second or third week in October.