I don't know much about colorectal cancer. But I think in general, in our experience, if you can eat mini ravioli and grilled cheese with tomato, then it's good to eat ravioli and grilled cheese with tomato. Whatever goes in.
We found that when you are having a hard time eating, we mixed up some Carnation Breakfast Essentials, with whole milk, a little extra powdered milk, and a scoop of ice cream or fruit sorbet in the blender to get through the bad times. My dad doesn't like the Ensure or Boost type drinks. Right now, he's not eating much at all. He can just about get one of those drinks down. Twice a week maybe he gets an egg or two in. Whatever goes in, and stays in, and provides a little extra protein if possible. You can even use this liquid with one of those Jello instant pudding mixes, and just substitute it for the liquid called for on the box.
Frozen fruit in the blender with those drinks is good too. You can change up the flavor. Right now, dad's favorite is the vanilla Carnation mix, with frozen peaches tossed into the blender. You can use bananas, berries, whatever you enjoy.