I have had a boat load of pecan that I got from a local widow. There are some pictures in a thread around here somewhere.
Here is the thread: http://woodtalkonline.com/topic/1395-a-craiglist-bandsaw-and-a-little-someting-extra
Anyway, color in pecan can range from a creamy color in the sapwood and butterscotch to an almost walnut brown in the heart, as you can see in the pictures in that thread.
I have gotten good results filling knots and voids with epoxy. I tint the epoxy a bit to match the color of the surrounding wood. Knots and voids are ususally fairly dark, so I use a little walnut transtint dye in the epoxy.
With air drying, you are more than likely going to experience some splitting from the ends. Get some sealant (or a thick coat of latex house paint) on the ends to help prevent that.
Another problem I have seen is boreholes in the sapwood (and frass) from wood-boring insects. I have filled boreholes with untinited epoxy with good success.
You will have to do your own research about pecan insects, based on your area. Call you county extension agent, that would be a good place to start.
Like others have said, get it stickered, dry and flat and forget about it for a year or so.