As others have mentioned it's about the mental association. For example, drinks and candies that are colored blue will not be repugnant to most people. Nor would things like blueberry muffins or blueberry pies. These are meant to be or perceived as dark blue or purple, so the mind says "Yummy." (Assuming that you like those foods." However, if peanut butter is blue, even though the consumer is told nothing is wrong, it will be perceived as bad or repugnant because it is not supposed to be blue, and the brain receptors recognize this.
I wonder if this is a cultural thing. Here in the US, there are kinds of food and drinks that are colored blue.
For example, a lot of people like "sports drinks" like Gatorade and Powerade. One of the popular colors in those drinks is blue. There are also blue candies, though only small ones like Skittles and M&Ms. So I do not think that there really is an aversion to eating blue foods -- just that there aren't many naturally blue foods so we don't associate blue and food.
The association of food with the blue color should be done very carefully.
Blue color reduces appetite and create repulsion. This thing happens because natural food is rarely blue. Most often, if it is so, then it is toxic, or simply spoiled.
On the other hand, the blue color has many qualities.
Blue relaxes the nervous system. It makes people contemplative, which is the opposite reaction to the red color.
For instance, light blue is a good color for bedrooms because it calms down.
In a blue environment, the productivity increases. Studies have shown that students get better grades if the place of their exams are blue rooms.
When people read a blue text, they manage to retain more information.