The video below shows the process in which vegetables, in particular, peas, is painted, and some red chemical is injected in a watermelon in order to make it intensely red and deceive customers with its looks. The chemical which is displayed in the video, erythrosine B, is usually used in confectioneries for some types of candy and gels for decorating cakes. It is actually an additive (E 127).
The American Association for Food in 1990 initiated a partial ban on the use of erythrosine because studies have shown that its excessive consumption caused cancer in mice.
For more information check the video below: