Change Color Scheme by clicking a link

Hello,

I’m trying to ‘showcase’ my WordPress theme, and I would like to create an option for the viewer to see the different color scheme options by clicking a link. I see many other demo themes doing this and I just can’t seem to figure it out.

Here is an example of what I would like to accomplish:
https://studiomommy.com/ellie-jane/

She has a “Theme Colors” option on the nav bar which drops down to display all the different theme options.

Any help would be greatly appreciated! Thanks!