Originally there were only two furs, ermine and vair. (The glass slippers of Cinderella were not "verre" but "vair" -- so they were fur slippers, squirrel fur slippers, such as were worn in mediaeval Europe.)  Ermine was white with the ermines' black tails scattered across the shield.  Vair was blue and white, notionally composed of squirrel pelts sewn together in such a fashion as to show the blue-grey back alternately with the white underside. Later the heralds invented varieties of ermine such as "ermines" for white tails (known as "spots") on black, "erminois" for black spots on gold, and "pean" for gold spots on black (these can be seen at http://www.baronage.co.uk/nl/nl-01-07.htm#SILVER )

Now what about white?  Is it a colour?  And if it is, is it quite different from the metal silver?  Or is it just an alternative to silver, used to represent it when the technology for true silver is absent, just as yellow is used to represent gold?

In the early days of heraldry white appears to have had no purpose other than to represent silver.  Early armorials used white (or the absence of any colour on a white page) instead of silver.  The Scottish Flag, "Azure a saltire Argent", undoubtedly bore a white St Andrew's cross.  An English Crusader's surcoat bearing the red cross of St George would be white in colour, not silver.  (In the development of heraldry, practicality was important.  In very early days it was difficult to produce a black that would not fade into blue, so black was not a  colour initially (and blue was quite dark).  For similar reasons, green and purple were less often seen because they were expensive, the former coming from Sinople on the distant Black Sea, the latter from rare shellfish.  White would be used instead of silver because it would be easier.)  The "red, white and blue" of the Union Flag (the "Union Jack" when flown aboard H.M ships) is of "Gules, Argent and Azure" heraldically, but no flag is ever seen with the white stripes painted silver.

As the centuries advanced, silver thread and gold thread became more readily available for costumes and for decorative banners, silver paint and gold paint for artists to work onto canvas and carvings, and thus Argent became truly silver and Or truly gold. Illuminated books by such as the Limbourg brothers glowed with their precious colour.  White was then merely the practical manifestation of Argent, effectively the poor man's silver.

But it did have a separate existence.  Vair, in the early days, before the varieties were invented, was only of blue and white (never blue and silver, Azure and Argent).  The arms of the Count of Guines were Vair.  The arms of the Duke of Brittany were Ermine - a white (not silver. not Argent) shield with black spots.

And in more recent times white has acquired another use.  The labels borne by members of the Royal Family to debruise the Royal Arms are blazoned as white, not silver.  These labels appear also on the Royal supporters, so that on the silver unicorn they would be invisible if they were themselves silver (the black outline around a charge is an artist's whim, for it is not blazoned).

So, confusingly, white exists in two ways.  It does have its own existence as a constituent colour of ermine and of vair, and it exists as the colour of a label on the arms of Britain's princes. But white is also an acceptable substitute for silver on flags and in paintings.

Accordingly, in view of its acceptability as a substitute for Argent, new armorial illustrations in the Baronage magazine will from September onwards use white instead of the pale silver-blue that has so discontented our artists.  We shall review this decision in March.