Night mode

[Patrick Cannon <pattrick_cannon yahoo com>]

Hi,

Many commercial astronomy applications have a "Night
mode" that basically gives a red or blue tint to the
entire screen to help the users night vision.

Does anyone know how to do this using GTK+ or GDK?
Can this be done with regular X calls?  

Could someone provide me a small example or point me
in the right direction?

Thanks for you help,
Patrick Cannon

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