To edit colors, you can open LESS file located at assets/css/style.less. But you need to compile LESS after that. For this reason you can use local LESS compiler or online compiler, for example - LESS2CSS. Otherwise you can replace all occurrences of the same color in CSS file located at assets/css/style.css
For example: main and default color of theme is #4caf52 and it's created as a variable @ThemeGreen.
If we give the variable another value @ThemeGreen:#af3e39;
Just changing one parameter - you change the color scheme of all pages