I have a town in my story where everything is white. Including the food. Apart from bleaching things white, they eat only white food and suffer from some diseases brought about by poor nutrition. Now, Seeing as how most Dairy products are white, they won't suffer from a calcium deficiency, but what would they not be eating? What are the nutrients they'd be missing out on and what diseases would they get as a result? Is it possible to Overdose on certain nutrients?
They would get scurvy from not having enough vitamin C which comes from citrus. Too much calcium can cause kidney stones. Probably might not get enough Iron. Vitamin C is important for Iron absorption. Protein doesn't absorb well when taken with calcium at the same time. There are many more and I will add them as I remember.
There's a number of root vegetables that are white, at least after they are prepared. You can get a lot of nutrients from them. White potatoes have a lot of vitamin C. I doubt you'd overdo the calcium from eating a lot of dairy, plus you'd get a lot of protein that you would need. White fish is pretty good stuff. If your a purist and demand a clean white then you could get rid of most of these foods.
Fish, pork, and chicken are white and do have protein, but they don't carry the iron that red meats do. Also, you can get iron from dark green leafy vegetables which are left out here. Many of the nutrients interact together and are needed for absorption. Eating only white food and drinking white drinks is also going to make it hard to get a lot of your other minerals.
Potatoes are not a good source of vitamin C, because they are nearly always eaten after cooking. Cooking reduces and/or destroys Vitamin C, so while potatoes start out with Vit C just underneath their skins, peeling and cooking effectively removes it. So does lengthy storage of any fruit and vegetables that you're planning to eat raw. Best sources of Vit C are very fresh fruits and vegetables, eaten uncooked, or very lightly cooked. When in doubt, good quality ascorbic acid supplements, used in moderation, are a good idea.
Did you try Googling white food? http://www.webmd.com/diet/features/truth-about-white-foods I'm sure you can find a lot more.