Run the screen diagnostic (hold D through powerup to get to that).  If the self-tests do not show the same effect, you may need to adjust the screen brightness and contrast. If the self-tests do show the same effect, is the screen identical to the original or is it a different model?  If it's identical, it may be defective;  contact your supplier for a replacement.  If the screen is a different model, it may simply have different display characteristics.  You'll have to contact your screen supplier to find out if they accept returns.  Note that most will not.  
I have replaced my dell inspiron laptop screen and now after replacement,....it looks slighlty yellowish and not how it used to look. need help with this. The night time mode is not on.
Laptop screen with a yellowish tint