What visual evidence might explain the differing gray appearance between a fresh nest and an older social wasp nest?

An extremely fresh nest will show a lighter, creamy color from newly processed wood sources, while older nests turn darker and mottled gray from gathering material from older sources like decomposing plant matter.

The coloration of a social wasp nest can serve as a subtle indicator of its construction history and activity level. When a colony is in its nascent stage early in the season, the workers utilize recently processed, fresh wood fibers, resulting in a pulp that dries to a light, almost creamy or white hue. As the colony expands rapidly during peak summer, workers become less selective about their raw materials, sourcing wood from whatever is accessible, such as old, weathered fence posts or decomposing matter. This variation in source material leads to the finished, older structure exhibiting a darker, mottled gray appearance.