This is something you will need to discuss with your surgeon, as unexpected complications can and do arise. The colon has a lot of blood vessels and you can potentially lose a lot of blood during the procedure. I required 2 blood transfusions after my surgery, but I was quite ill with UC and had already lot a lot of blood (post opt my hemoglobin was a staggering 5.2). I also required a plasma transfusion before the surgery. Plasma is a blood product and would carry many of the same risks as a blood transfusion.
That being said, you can self donate prior to surgery, if you well enough going in.