Gules

In heraldry, gules () is the tincture with the colour red. It is one of the class of five dark tinctures called "colours", the others being azure (blue), sable (black), vert (green) and purpure (purple).
In engraving, it is sometimes depicted by hatching of vertical lines. In tricking—abbreviations written in areas to indicate their tinctures—it is marked with gu..
Etymology.
The term "gules" derives from the Old French word , literally "throats" (related to the English "gullet"; modern French ), but also used to refer to a fur neckpiece, usually made of red fur.
A.C. Fox-Davies states that the term originates from the Persian word , "rose", but according to Brault, there is no evidence to support this derivation.
Examples.
Gules is the most widely used heraldic tincture. Through the sixteenth century, nearly half of all noble coats of arms in Poland had a field gules with one or more argent charges on them.
Examples of coats of arms consisting of purely a red shield (blazoned "gules plain") include those of the d'Albret family, the Rossi family, the Swiss canton of Schwyz (prior to 1815), and the old coats of arms of the cities of Nîmes and Montpellier.