Pink background and loss of font clarity

Win 10 Pro version 10.0.18363.
I recently changed my Theme and shocked to find that there is a general "haze" in every browser window. The fonts are now greyish. No matter what I try I just can't seem to get back to a crisp, white background and black fonts. Most annoying is the pink. Here are a few examples:

Quite frankly, I'm terrible with changing the settings such as colors, etc. Any help getting things back to default settings would be great.

I only see pink in the default Gmail theme, and the fonts look black to me.

Thanks for the replies, gentlemen and I apologize for the late replies. I got tied up with our home closing. I tried Specify Default Desktop Background in Windows 10 and It did nothing for the appearance within a browser....still pink in areas such as login button, search boxes, etc. The fonts still appeared grey. NMI and Jacee......the pic I sent is the default Gmail theme with that god-awful pink.

The last pic I inserted is the best example of the haziness and blurred fonts. It's screenshot from the tenforums page on instructions for uploading images.

Thanks again.