Colors Are Not Good

[cppvan]

Hi,

I'm new here and don't know very much from android tablets. I'm normally a apple user.
Still, my son got an Astar QuadCore-A33 tablet from his grandmother for his birthday.
At start, everything goes well, but today I sow that the colors where not good anymore.
After I checked the brightness, I could not fix the problem.
Can somebody tell me how I get the colors back to normal.
Thx,
Chris