The colortype filter is deprecated. Use piecename instead. The colortype filter takes one argument, a set filter. If its argument represents a set with exactly one square, then the value of the colortype filter is a number that represents the color and type of the piece on that square:

  x=colortype a1
  y=colortype h1

If the argument set filter does not represent a set that has exactly one element, the colortype filter does not match the position.

Otherwise, suppose s is the square represented by the argument set filter. Then:

  1. If s is not occupied by a piece, colortype s is 0.
  2. If s is occupied by a white piece, then
    colortype s == type s 
  3. If s is occupied by a black piece, then
    colortype s == - type s