Green’s Dictionary of Slang

(US drugs) light-coloured Colombian marijuana.

1976		R. Sabbag Snowblind (1978) 230: He opened up a brick of the strangest-looking marijuana Swan had ever seen. It was white. . . . Rubia de la costa, the blonde from the coast, the finest, complete dynamite ‘up’ grass in the world.
2001		ONDCP Street Terms 18: Rubia (Spanish) — Marijuana.