XGetWMColormapWindows(3) on Linux
The text aab747e0f5bd, as Debian 10 (Buster) shipped it.
set or read a window's WM_COLORMAP_WINDOWS property
The text aab747e0f5bd, as Debian 10 (Buster) shipped it.
set or read a window's WM_COLORMAP_WINDOWS property