I would stay away from carrot juice and oranges. They have lots of Sugar in them and cancer loves sugar. Juice greens and mix it half and half with Celery or cucumber juice to make it more drinkable. A little ginger adds flavor and is good for the digestion.
I was on a raw diet for a while, after I got done with my chemo and radiation. Lots of people who have had cancer swear by it. It helps to clean out the bowel and the liver, so the body can expel toxins, and it supports the immune system. Some people have difficulty digesting an all raw food diet, and I'm not sure if having colon cancer is going to make it hard. Perhaps digestive enzymes would help - at least that's the recomendation I got from my colon hydrotherapist.