A mix of levels of red, green, and blue creates basically any color imaginable. In GMT each color can be represented by the triplet /
/
. For example, 127/255/0 (half red, full green, and no blue) creates a color called chartreuse. The color sliders in the graphics program GIMP are an excellent way to experiment with colors, since they show you in advance how moving one of the color sliders will change the color. As Figure I.1a shows: increase the red and you will get a more yellow color, while lowering the blue level will turn it into brown.
Is chocolate your favorite color, but you do not know the RGB equivalent values? Then look them up in Figure I.2 or type man gmtcolors for a full list. It's 210/105/30. But GMT makes it easy on you: you can specify pen, fill, and palette colors by any of the more than 500 unique colors found in that file.
Are you very web-savvy and work best with hexadecimal color codes as they are used in HTML? Even that is allowed in GMT. Just start with a hash mark (#) and follow with the 2 hexadecimal characters for red, green, and blue. For example, you can use #79ff00 for chartreuse, #D2691E for chocolate.