in Thoreau’s Journal:

The fields are blued with blue eyed grass a slaty blue. The epilobium shows some color in its spikes. How rapidly new flowers infold—as if nature would get through her work too soon. One has as much as he can do to observe how flowers successively unfold. It is a flowery revolution to which but few attend. Hardly too much attention can be bestowed on flowers. We follow we march after the highest color—that is our flag—our standard—our “color.”  Flowers were made to be seen not overlooked. Their bright colors imply eyes—spectators.—