SoGLColorIndexElement(3) on Linux
The text 4b5a41d7226d, as Debian 7 (Wheezy) shipped it.
The SoGLColorIndexElement class sets the current OpenGL color. This element is only used when the OpenGL canvas is in colorindex mode, ie where colors for individual pixels are fetched from a color lookup table ('CLUT'). The usual thing to do is to set up a canvas in RGBA truecolor mode.