"These figures [on the piers] were all painted in reds, blues, and yellows. In applying color, every change of color required a change of plane. Palenque sculpture is linear in style, even when it acquires a three-dimensional quality. The outline requires the eye to follow the form, and cannot be detached from it.
George Kubler points out that "iconography is spatial and visual," and that "it conveys conventional or agreed meanings." Palenque's iconographic sculpture was the visual content of the spoken word. Color, through the medium of stucco sculpture, developed into an iconographic language. Painted stucco sculpture was not just a work of art, but it was a speaking work of art, one bound by a rigid framework of specifications.
Background areas of piers, buildings both inside and out, bodies of humans including their hair and major portions of their clothing, and human like parts of serpent bodies were all painted red, albeit different shades. Red was the color of the living world. Blue was designated the color of things divine, motifs pertaining to the rights of kings, to things precious such as jade and quetzal feathers, divine beings such as serpent-footed babies (God K), and dwarfs. Yellow was reserved for motifs pertaining to the underworld such as jaguar tails, crosshatched areas, underwater plants, and the portions of serpents (dead scales)."
Merle Greene Robertson, Sculpture and Murals of the Usumacinta Region, in MAYA [Palazzo Grassi, Venice 1999] p.300