You may have turned on a setting by accident during the repair. Follow these steps:
# '''Go to Settings'''
# Tap on the gear icon on your home screen or app drawer to open the Settings menu of your device.
# '''Open the Accessibility options'''
# Scroll down and tap on “System Settings”, then tap on “Accessibility.”
# '''Invert the screen color'''
# Tap “Negative colors” to turn off this option.