Those plants that do appear blue are in fact often using a red pigment known as anthocyanin. Through pH shifts and a mixing of pigments, combined with the reflection of natural light, the plants are able to generate the appearance of a naturally occurring, blue color. That's the reason why plants such as bluebells, hydrangeas and morning glories appear various shades of blue, when in fact, as Lee explains, "There is no true blue pigment in plants."