I am not sure why this qualifies as a front page article. To achieve color schemes in CSS only follow these steps.
1) Remove ALL color information from your CSS files and relocate that into a new CSS file only for color information. That is your default color scheme.
2) In that color scheme file prefix each rule with the same class name, possibly colorDefault.
3) Create a second color only CSS file with dark colors. This is your dark color scheme. Change the colorDefault class name to something else, possibly: colorDark.
4) Include those color files in your site using either media queries from the primary CSS or link tags in the HTML.
5) Finally add class name colorDefault to your HTML body tag. Use JavaScript to change that one class name as the user selects a different color scheme on user interaction.
1) Remove ALL color information from your CSS files and relocate that into a new CSS file only for color information. That is your default color scheme.
2) In that color scheme file prefix each rule with the same class name, possibly colorDefault.
3) Create a second color only CSS file with dark colors. This is your dark color scheme. Change the colorDefault class name to something else, possibly: colorDark.
4) Include those color files in your site using either media queries from the primary CSS or link tags in the HTML.
5) Finally add class name colorDefault to your HTML body tag. Use JavaScript to change that one class name as the user selects a different color scheme on user interaction.
Here is an example:
https://github.com/prettydiff/share-file-systems/tree/master...