petrol blue

Noun

 * 1)  A greyish blue colour, tinted with green.

Usage notes

 * Many people erroneously believe that this is a misspelling of petrel blue, and that the term refers to the sea bird. However, the OED gives only this spelling. The term may originally have pertained to petrol-derived compounds such as paraffin, which is often coloured blue.

Adjective

 * 1)  Of a greyish blue colour, tinted with green.