Explain that antocyanin is a pigment aften responsible is the red color

One explanation can be that its chemical makeup allows it to absorb all wavelengths of light not responsible for the red color, as in it absorbs all colors but red. To be more accurate though it depends on the PH to what pigment it gives off do to its specific R groupings it can turn purple, blue, or red depending on the PH, if it is red most of the time then it is naturally surrounded or submersed in the PH that allows it to react and be red. In plants it is an adaptation to avoid being eaten. I honestly don't know what field you are talking about so I hope this helps, but this might not be what your looking for sorry.

Compound with sulfer  is bright red