I like your question. I thought the other colors appeared when the chlorophyll disappeared - that the other colors were there in the green leaves, but the green chlorophyll hid them. It turns out I'm right, but only for the yellow [xanthophylls] and orange [beta carotene] pigments. The red and purple[!] pigments are first synthesized by the leaves in the late summer, when the chlorophylls disappear. The chlorophylls degrade into colorless molecules called tetrapyrroles. Wikipedia has a nice article about this - Autumn leaf color

When we eat beta-carotene (in orange food, like carrots), some of it is converted to Vitamin A in our bodies. Vitamin A is an important molecule for vision, in the retinas of our eyes.