edible/drinking items with colors such as blue and black are less desirable for eating or drinking;usually red and green increase appetite.

So why is it that Coke is so desirable, even with children, despite its color?
-MC

4 answers

Here are my personal unscientific thoughts about your interesting question.

The only red drinks I like are V8 (with a dash of worcestershire), Singapore Sling and Bloody Mary. There used to be a popular soda fountain drink called Green River. I used to like Hawaiian Punch and Nehi Strawberry (both red) but not anymore. All I remember is the cloying sweetness. Green River may have lost popularity because of all the food coloring it contained.

People like Cokes because they taste good and have a kind of battery-acid "kick". At least the Coca Cola Classic still does.
To add to Drwls's thoughts --

Aren't "appetizing" colors a matter of habit and culture?

To me, Coke is dark brown. Think of these popular brown foods -- hamburger, barbecued ribs, chocolate, baked potatoes, coffee, toast.

Would you want to eat green meat, eggs (despite Dr. Seuss), or butter?

During World War II, butter was rationed, so people switched to margarine. However, the dairy industry influenced the laws that prohibited the sale of yellow margarine and only white margarine was sold. We mixed it with a small capsule of yellow food coloring to get yellow margarine. One time my mother mixed the white margarine with green food coloring. That mixture turned off the family -- and she never tried anything but yellow margarine again.
Yes but some foods like herbs are green, and sauces are red.
I get the general point though..thanks :)
-MC
An "instinctive" preference for red and green may have evolved during and following the early days of hunter-gatherers. red = meat (or blood) and green = edible plants.