Those Nokia engineers it seems are always busy, busy, busy.
Their latest enhancement to the Nokia Lumia 920 is a new feature added to their Display and Touch device-specific settings app.
The app allows one to set the colour temperature of your display, from cold and blue to warm and red and anything in-between. I am not sure who asked for this feature, but I don’t think anyone will say no to more customizability for their phone.
The feature does not appear to be present on all handsets, and may need specific firmware.
See if your handset qualify by downloading the app using the QRCode right or clicking this link.