Juan O'Gorman covered four windowless facades of UNAM's Biblioteca Central — some 4,000 m² — in natural stone. He refused paint: outdoors, paint fails. Instead he drove around Mexico collecting ten to twelve colours of rock from Guerrero, Guanajuato, Hidalgo and Zacatecas, sorted it by colour, and set the mural in one-square-metre panels.

The result reads flat, dry and matte from a hundred metres. This system inherits that discipline. Colour comes from stone, not from light. Blocks tessellate and butt edge to edge along a mortar hairline. Nothing glows, nothing gradients, and the single blue on screen is glass, because no stone gave him one.