Secondary colours are purple, green and orange.They are made by mixing the primary colours together eg red + yellow=orange, blue + yellow = green, red + blue = purple.
I discovered they are found throughout a wide variety of printed media as they convey open and board connotations. However, when compared to primary colours they are more mature and sophisticated.
I also noticed secondary colours are found commonly in Thai Food advertising. I think this is because the fresh, zangy flavours of Thai food can be represented through the organic green and bright orange colours.
