Why is red dark?

The color read used in many painting a long time ago have darkened a lot since the time that they have been painted. Researchers thought otherwise until 2 scientists disapproved the other theory and made their own. The color red contains vermillion which is a made from a mineral called cinnabar. This mineral is made up of mercury sulfade. Researchers showed that when that was exposed to chloride ions such as salt it absorbs causing the mercury to become metallic which is black in color. This was probably what cause the dark color of red paint because it was found in the red paint. I think this was an interesting observation, although i do not go to many art museums i never noticed the color differences from out time to when they painted it.




 http://www.scientificamerican.com/article.cfm?id=vermillion-red-paint-darkening-physics