Editing CSS
Without the help of .css files, your website will remain a boring black and white forever. Go to "style.css" in the site files and press edit.
Colors and fonts can we changed for your website in the "body". The colors are given in hex codes, which you can use a color picker to find the hex code for colors you want to use.
To change your font, you have to either download a font from somewhere like DaFont, or source it from somewhere like Google Lapis. They both have their own instructions to go along with them.