If there’s one color that is almost universally associated with nature, it’s green (just don’t tell the mammals). No prizes for guessing why – green is overwhelmingly present in the plant kingdom. Once we start thinking about fruits and flowers, more of the rainbow starts to emerge, but with one notable exception. Where is all the blue? Now, we’re not claiming there’s no blue to be found among plants. Several common garden varieties – like hydrangeas, cornflowers, and delphiniums – come in true blue varieties, and striking rarities like the aptly named sapphire tower plant fly the azure flag. …