Red Foods
There are two types of red foods. Those which are always red, and those which become red if you eat too much of them.
Crisps / Chips
Crisps as they are called in UK & chips in US are red. They are red because they are always bad. That is, they have a lot of calories and the calories they have are bad. There is nothing in a crisp that you cannot get in a much healthier way somewhere else.
And the thing about most if not all crisps is that they are moreish, that is, it is almost impossible to have just one. If you have one, you have the packet. And as manufacturers are making bigger packets this is particularly bad.
Take Aways
Most take away food is red. Pizza, curry, burgers are all red most of the time. Occasionaly they are not too red, but then they can be very red.