Colormap Tk_GetColormap(interp, tkwin, string)
These procedures are used to manage colormaps. Tk_GetColormap returns a colormap suitable for use in tkwin. If its string argument is new then a new colormap is created; otherwise string must be the name of another window with the same screen and visual as tkwin, and the colormap from that window is returned. If string doesn't make sense, or if it refers to a window on a different screen from tkwin or with a different visual than tkwin, then Tk_GetColormap returns None and leaves an error message in interp->result.
Tk_FreeColormap should be called when a colormap returned by Tk_GetColormap is no longer needed. Tk maintains a reference count for each colormap returned by Tk_GetColormap, so there should eventually be one call to Tk_FreeColormap for each call to Tk_GetColormap. When a colormap's reference count becomes zero, Tk releases the X colormap.
Tk_GetVisual and Tk_GetColormap work together, in that a new colormap created by Tk_GetVisual may later be returned by Tk_GetColormap. The reference counting mechanism for colormaps includes both procedures, so callers of Tk_GetVisual must also call Tk_FreeColormap to release the colormap. If Tk_GetColormap is called with a string value of new then the resulting colormap will never be returned by Tk_GetVisual; however, it can be used in other windows by calling Tk_GetColormap with the original window's name as string.