This solution may only works if the device not suffered like cracked lcd screen. You may only need to buy a new lcd screen replacements and replace a broken lcd screen.
You may refer to the solution below and follow some procedures on how we troubleshoot this kind of LCD display problem if occurred on device when suffered wet damaged or accidentally heavily dropped.
Nokia 6600 slide LCD display screens problem solution
1. Buy lcd screen replacements for a damaged or broken lcd screen and replace it.
Check the lcd flex cable, ensure that cable ribbon is properly pinned to the connector.
Replace the whole ribbon cable assemblies if damaged.
2. For white screen and blue screen display, try to restore and flash update the device firmware to any latest version available.
3. Check the LCD screen pin connector, replace if it's damaged, clean it if there is an oxidation build up found.
4. For garbled, saturated screen display replace the EMI-ESD filter Display IC.
5. For dark screen or black screen this may oftentimes cause by the LCD display backlight white LED failure, just see how to troubleshoot the nokia 6600 slide LCD backlight LED here.