How do I revert a negative black and white screen with tiny letters on my Mac?

Mac 21.5” 2017 High Sierra Telemundopr en vivo ahora computer screen has turned black and white only with tiny letters that are barely legible.

I tapped a button on the computer to enlarge the letters. Instead the screen now looks like a negative black and white photo that is not very defined. Looked for a @reverse button” that would restore the page to normal, but cd not find any. Am not a techie n have no idea how to revers the look of the page. How someone can help me with simple instructions that I can follow to revert this issue.ith this limited info,

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