Colour variance may occur as the result of a token cascade
or, more interestingly, a chromatic shunt
. There are two possible forms of colour variance, either of which may be provoked by these methods. The most common result is a shift in the colour of podumes or tokens
, usually resulting in a moderate decrease in podume value. For example, blue tokens may shift to red, black to green, gold to silver, and so forth. The magnitude of the effect depends on the size of the cascade or pickering, and this is easy to predict. The rarer result is when the colour of the actual lines is shifted (for example, the Circle line may be shifted from Gold to Silver, thus overlaying the Jubilee line), and the station values on the shifted lines are altered by a corresponding amount. Some of the most elegant wins the game has seen have been achieved by causing a colour variance at the correct time; Boris Baryshnikov
is generally considered to be one of the best players in this style, while Ruttsborough
gained much of his notoriety by brutally exploiting the letter of the colour variance rules for his own purposes, while thoroughly trampling the rules' spirit.