Here's the Nokia 1508 solution for display problem, like blue screen, blank or white screen, saturated or garbled LCD screen displays. This may help if the device already calibrated through firmware flash update and already been replaced the LCD module but the problem still exists.
If the device firmware is okay and already tried replacing a new LCD on the device and it doesn't solved the problem , you may refer to this solution below and do have a hardware check up and test procedures.
Nokia 1508 No Display problem Solution
To fix the problem you may first check the LCD pin connector for possible damaged and oxidation build up, clean or replace it if necessary. Then check each of the filter resistors since its the most vulnerable components connected on the display circuit. The bypass capacitors too may caused the problem if faulty or damaged, you may also check each one of those components. The display data signals is feed from the CPU chip, there is also a possibility that the display is caused by a faulty CPU IC in most serious cases problem like wet or water damaged device.