4.2.3 Color expressions

Colors expressions are hybrids between fixed-length braced expression-lists and strings:

color-expression:
  string |
  { expression, expression, expression } |
  { expression, expression, expression, expression } |
  color-option

The first case permits to use the X Windows names to refer to colors, e.g., Red, SpringGreen, LavenderBlush3, … (see ‘Common/Colors.h’ in the source code for a complete list). The second case permits to define colors by using three expressions to specify their red, green and blue components (with values comprised between 0 and 255). The third case permits to define colors by using their red, green and blue color components as well as their alpha channel. The last case permits to use the value of a color-option as a color-expression. The various color-options are listed in Options.

See ‘t3.geo’, for an example of the use of color expressions.