• download the whole repository as zip file and unzip it.
• Open your firefox browser.
• In the url bar, type about:profiles and press enter.
• Go to root folder of the profile default release section.
• There click the open folder option. This will direct you to your file manager .
• Now copy and paste the User.js file there.
• Then, make a chrome folder and paste all the files from the downloaded chrome folder inside the new chrome folder.
• Close the Firefox browser and reopen it. All the changes will be applied.

This is the color scheme i am using with firefox . If you want to use it, download Firefox Color extension first then click the given link of color sheme. You can automatically apply it and customize it as you wish.