They have have a much larger and thicker flake, but more importantly look at the ingredients.
Ultra Color
Analysis: Min. Protein - 47%, Min. Fat - 14%, Max. Fiber - .7%, Max Moisture - 4.5%. Spray Dried Salmon, Special mix of plankton, krill and brine shrimp, Astaxanthin and Canthaxanthin from natural sources, Spirulina Powder, Carotene from natural sources , Dried Yeast, Wheat, Oat and Gluten Flours, Fish Oil, Lecithin, Vitamin and minerals. No Preservatives.
and Tetra Color Plus
Fish Meal, Dried Yeast, Shrimp Meal, Ground Brown Rice, Wheat Gluten, Feeding Oat Meal, Fish Oil, Soybean Oil, Potato Protein, Algae Meal, Sorbitol, Lecithin, Monobasic Calcium Phosphate, Yeast Extract, Ascorbic Acid (source of Vitamin C), Inositol, Niacin Riboflavin-5-Phosphate (source of Vitamin B2), A-Tocopherol-Acetate (source of Vitamin E), D-Calcium Pantothenate, L-Ascorbyl-2-Polyphosphate, Thiamine Mononitrate (source Of Vitamin B1), Pyridoxine Hydrochloride (source of Vitamin B6), Vitamin A Palmitate (source of Vitamin A), Menadione Sodium Bisulfite Complex (source of Vitamin K), Biotin, Vitamin B12 Supplement, Cholecalciferol (source of Vitamin D3), Manganese Sulfate Monohydrate, Zinc Sulfate Monohydrate, Ferrous Sulfate Monohydrate and Cobalt Acetate.
Color Includes: Beta-Carotene, Annatto Extract, Blue No. 2 Lake, Canthaxanthin, Red No. 3, Yellow No. 5 Lake and Yellow No. 6 Lake. Ethoxyquin as a preservative.
I am not sure what some of this is.
As for the color enhancers (and yes they are needed for the oranges, reds and yellows) the Tetra is missing Astaxanthin lock stock and barrel which is the main one for oranges and comes from algae grown for the process or the krill that eat this particular algae. They instead substitute what looks like food dye names. My guess was they tried spray paint and the fish did not eat it lol. The only natural color enhancer comes from the salmon they used to make the flake. Granted the fiber is low on the Ultra Color, but I would rather that than the rest of the garbage.