Is there not a way for each individual to customize their background? So those who like this can keep it while others can switch to a different color?

There isn't an option on create-a-forum for users to pick their own 'style' setting.

If you wish, you can go into their Support Forum ->Suggestions and ask them to offer this option.

http://support.createaforum.com/ 

However, If you're using a FireFox browser there is a quick way for you to customize the background color +/or the text color and the 'zoom' level. 

It's called the NoSquint add-on and it works great. 

I just tried it and I was able to change the background to white, the text to black, and adjust the 'zoom' level for the text which could be easier on your eyes.  You can even change the text color of the 'links' too. 

JhonJeter could even change to colors scheme to match his Seattle Mariners or Chicago Cubs jammies using this add-on.

more info here: https://addons.mozilla.org/en-US/firefox/addon/nosquint/

https://urandom.ca/nosquint/

Hope this helps.