As an heraldic colour, the word azure simply means "blue". It is one of many concepts with both a French and Germanic word in English, the former being used by the French-speaking nobles following the Norman Conquest of England in 1066 and the latter being used by the commoners of Anglo-Saxon stock. So while French-speaking heralds described banners as azure, commoners simply called them blue. Because it comes from a French word that simply means "blue", a wide range of colour values is used in the depiction of azure in armory and flags.
In addition to the standard blue tincture called azure, there is a lighter blue sometimes found that is called bleu celeste or "sky blue". Neither azure nor bleu celeste is precisely defined as a particular shade of blue, but azure is consistently depicted in a much darker shade.
Sometimes, the different tinctures are said to be connected with special meanings or virtues, and represent certain elements and precious stones. Even if this is an idea mostly disregarded by serious heraldists throughout the centuries, it may be of anecdotal interest to see what they are, since the information is often asked for. Many sources give different meanings, but azure is often said to represent the following:
Arms of Dolní Přím municipality, Hradec Králové District, the Czech Republic.
Arms of the Dollern municipality
Arms of the municipality of Holtorfsloh, Seevetal, Lower Saxony.
Arms of St Cleere family of St Osyth, Essex.