Vantablack. This is the darkest color in existence, only 0.035% of light can pass through it. The light that does pass through it is eventually absorbed into the material. People who have seen it in real life say that it is actually impossible to look at and see any semblance of shape or contour.
"The eye just sort of slides off of it, as if looking into an abyss of nothing"
This is also the color of many ex’s hearts.