The first 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.