The classroom slate blackboard — first dark-gray slate, later porcelain-enamel in its signature green — is a matte surface dusted with white chalk and the ghostly streaks of an eraser. Wikipedia documents "Blackboard Green" as #274C43, the deep black-green that carries looping chalk script.

This design system distills that vernacular: a genuinely dark slate ground, hand-written headings in white chalk, pale-green annotation smears, and diagrams drawn as if pulled freehand across the board.