The rule of tincture is the most important rule in heraldry. It is very simple: “Color shall not be placed on color, nor shall metal be placed on metal.” However, it is not absolute, and can often be regarded as a guideline rather than a strict rule.

The two metals are silver (white) and gold (yellow). The four colours are red, blue, black, and green.

Furs are neither colors nor metals: A fur can be placed on a color, metal, or another fur. Furthermore, red can be counted as copper, and as such be placed next to a(nother) colour.

Certain blatant violations of the rule are used to denote exceptionally holy status (e.g. the arms of the Kingdom of Jerusalem, Vatican City, and the Holy See.)