Rambo Theme comes with five preset colors and two layouts (Wide & Boxed). You can create your own color theme using color picker. You can find this setting in Theme Appearance Customize. You have to no need any code customization. In this theme, we just want to offer visitors color variations. Now I will tell you how to change color schemes? Do following tutorial. Refer attach the screen shot.
1. How to Change Theme Color Scheme?
Go to => WP-Menu => Appearance => Customize => Theme Style Setting
Here you can see the Theme Color Schemes and Layout (Wide and Boxed). There are 5 colors for choosing and custom color. You can switched color & layout any time. Refer attach the screen shot.