Red wine is made from red grapes, but the juice of most types of grapes (red and white) is not discolored.
The process responsible for the color of the wine is called maceration. Literally, it is the retention of the juice by the solid parts of the grapes - zips, seeds, sometimes parts of clusters. In this process tannins, dyes and aromatic compounds are extracted. Depending on the variety and duration, the color could become more saturated and dense.