Welcome To AndroidCentral Hopefully we can get you sorted.
As L0n3N1nja said, Could you let us know what phone you have?
Some phones have different ways of accessing the "Reversed Colours" option.
Samsung Galaxy S4 Instructions (Example)
On any screen, swipe down the top of the screen to open up the notification panel and then tap the settings icon (Little Cog).
Scroll down to the Personalisation section and then tap Accessibility .
Tap Vision.
Scroll the screen to the bottom and then clear the checkbox next to Negative colours to disable this option.
The screen colour will be reversed back to the default and the text will be displayed black on white.
Hope this helps
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