I have the same screen.
Tap your on/off button...a quick access menu will come up.
In the menu there is a line where you are given 4 choices (I think) of what screen mode you want to be in.
You are more than likely in nighttime mode. You can tap the day button or the A button which the screen should swap either/or depending on the amount of light or time of day. Not sure if it has a light sensor or not.
Quick access menu is nice as you can quickly adjust screen brightness et cetera.