Rule of tincture

The rule of tincture is a design philosophy found in some heraldic traditions that states "metal should not be put on metal, nor colour on colour". The rule has been widely adopted by heraldic authorities and has been described as 'definite' and 'practically unbreakable'. However, the rule has also over time been significantly read-down, both by a narrowing of that to which it applies, and by the adoption of many exceptions. Thus, heraldic furs (such as ermine and vair), and animals and other charges represented "proper" (in their natural colours), are generally exempt from the rule of tincture. Certain elements of full heraldic achievements (for example, crests, supporters), and a variety of components in coats of arms (for example, bordures or animals' claws), are not covered by the rule.