Graphics Related Problem

I bought Dell  Insprion 15 3000 Series

My Problem is that when i open a new tab, and the background is white the screen is a bright

But when a webpage loads and the background is black or blue (dark color), the screen light gets a bit dark.

What could be the problem? I have Intel HD graphics and Nvidia Geforce. Intel i5 core 4th gen.

I hope i could make my problem clear.