A low residue diet is a low fibre diet. It is to help reduce the bulk in the bowel so that the inflamation can reduce. If you google low residue diet there are some sites with a large list of low residue foods. It's actually not to bad. Lean meat like chicken, steak is not recommended as it is hard for the body to break it down, fish, potatoes, carrots, eggs, white bread, plain scones, cheese, no green veggies, no pulse fruits, no bran...there's quite a list of foods to choose from to be honest. It does all seem daunting I know but with some determination you can find lots of foods you can eat on the low residue diet.
if you have trouble finding it I'd be happy to email you the list I have, although I got it via google, first on the list.