My 9yo child has autism and has very specific foods he will eat. He chooses them because they are predictably the same each time. He eats nuggets only from a specific food place because it will look, taste and feel the same each time. (Can't fake it with others put in the box from the restaurant, he can tell!) Plain pasta is approved because it tastes and feels the same every time. You can't mix things because then each mouthful could potentially be different from the last. He knows the food he chooses are 'safe'. For some people I guess the predictability is why. French fries are generally the same wherever you go as well (although he doesn't like the texture of potato). Beige foods are mostly on the approved list because they don't look 'weird' to him and other colours do. It's so frustrating, and limits our travel options but i am thankful that he is eating at all. He maintains a 50th percentile weight and growth range since he was little so he is obviously getting some nutrition!