My aim is to define those 4 color variables into the style.css file.
Then, use the variables into the css code, and also into third party plugin for customized css.
I followed this guide:
I need to define some color as variable because I need to change often the colors of the site.
So, it is a lot amount of work every time change the hex color value into the entire css file for every element, so using color variables will let me just change the hex color codes into the first definition, and the changes will be cascaded into the entire css file and will update the site in very short time.