When I run any component of JExpress on my Linux machine, I see, "Warning: Cannot allocate colormap entry for default background".

You may see this Linux error message when you try to run a JExpress installer, or any other Java program that uses a graphic interface. It means that your XWindows configuration file, XF86Config, is misconfigured. The video display driver must have a default color depth of at least 16 bits. Remove any lines in the Monitor section that specify a shallower depth.
Applies to
colormap, XWindows, XF86Config

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