How to add multiple css styles to a website?

Question

css

How to implement a user style change on the site, for example, there are three buttons red, green, yellow, respectively, when you click on any, the tone of the site changes, how to implement this?

Answer 1

www.w3schools.com/js/js_htmldom_css.asp
stackoverflow.com/questions/507138/how-do-i-add-a-...

Answer 2

For each css style, you make your own id by which you enable or disable styles through js