That’s a tough one because there can be so many reasons for colitis. For some dogs, increasing fiber helps, but for others(I think most) going as low fiber as possible is the key. Does the vet have your dog on I/D? If so, I would get a small bag of something relatively bland like NutriSource and start a VERY slow transition, like only 10% new food. Watch stools very carefully for any signs of stomach upset before increasing the amount. Other foods to try if NutriSource doesn’t work out are Abady and Victor’s Ultra Pro. They are both high calorie foods and will need a slow transition, but they are pretty low on fiber.
