Bleu celeste ("sky blue") is a rarely-occurring tincture in heraldry (not being one of the seven main colours or metals or the three "staynard colours"). Initially considered to be European rather than English or Scottish, after the Second World War it became more prevalent in England in badges of coats relating to the Royal Air Force, or the arms of those with some RAF connection. While in the post-WWII period bleu-celeste is depicted as a darker shade, in prior times it was depicted as very light, and has even been treated as a metal, as azure charges have been placed on a bleu celeste field, and vice versa.

Bleu celeste can be seen in the arms of (http://www.mad-alchemy.com/hsc/tress1.htm) the Canadian Governor General Ray Hnatyshyn.