Rule of tincture

The most basic rule of heraldic design is the rule of tincture: metal should not be put on metal, nor colour on colour (Humphrey Llwyd, 1568). This means that Or and argent (gold and silver, which are represented by yellow and white) may not be placed on each other; nor may any of the colours (i.e. azure, gules, sable, vert and purpure) be placed on another colour. Heraldic furs (i.e. ermine, vair and their variants) as well as "proper" (a charge coloured as it normally is in nature) are exceptions to the rule of tincture.

The main duty of a heraldic device is to be easily recognisable. Certain tincture pairs are difficult to distinguish when placed atop or over each other. Specifically, a dark colour is very difficult to distinguish if it is placed on top of another dark colour, and likewise a light metal is very difficult to distinguish on top of the other light metal. Though this is the practical genesis of the rule, the rule is technical and appearance is not used in determining whether arms conform to the rule. Another reason sometimes given to justify this rule is that it was difficult to paint with enamel (colour) over enamel, or with metal over metal.

The rule of tincture does not apply to furs, nor to charges blazoned "proper" (displayed in their natural colour, which need not be a normal heraldic tincture). The blazoning of a charge "proper" can therefore be used as a loophole when its natural coloration equates to or approaches another heraldic tincture it is desired to overlie. An example would be a white horse proper, since without breaking the rule of no metal on metal it could be placed on a field Or (gold), but a horse argent (silver horse), although visually indistinguishable, could not.

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