This is surely something the old glaziers understood, those who worked on the stained glass in the great cathedrals of Europe.  If people wanted simple light, they would have instructed the glaziers to give them clear glass, and that would be that.  If they wanted mere colors, they could have said, “Put a blue window here, and a gold window there, and a red window in front.”  But they wanted the glow and the gladness: they wanted intelligence and a profound joy.