In the Bön Buddhist tradition, the color blue has great, meaningful significance.  Specifically, the blue of the clear, open, vast expanse of the sky.  Among the five schools of Tibetan Buddhism, only Bönpo monks have blue on their robes.  In ancient times, Bön practitioners wore blue robes.  Bön texts are wrapped in blue cloth, the stiff top and bottom covers which protect the paper are blue, and all page edges are painted with blue ink.  Here, a sacred scripture is written on blue paper.