glutCopyColormap copies the logical colormap for the layer in use from a specified window to the current window.
void glutCopyColormap(int win);
glutCopyColormap copies (lazily if possible to promote sharing) the logical colormap from a specified window to the current window's layer in use. The copy will be from the normal plane to the normal plane; or from the overlay to the overlay (never across different layers). Once a colormap has been copied, avoid setting cells in the colormap with glutSetColor since that will force an actual copy of the colormap if it was previously copied by reference. glutCopyColormap should only be called when both the current window and the win window are color index windows.