Although colors are a critical characteristic in lichen identification, they are also highly variable between specimens, lighting, screens and eyeballs. The Lichen Color Chart attempts to show the variation of colors and within a color. Note: if your device/monitor is not color calibrated, of course the colors will be skewed.
Special: Pale Yellow Green
This subtle but critical color in lichens indicates the presence of usnic acid, a secondary chemical which is very helpful in identification. In shade, it may look like green with a hint of dirty pale yellow. In sun, it may look more like a dirty pale yellow with hint of green (like chamomile tea). Learning to see this color is very helpful in identification but not always easy.