The Skins manager section of the admin panel is where you can change the layout, colors, background images and fonts of the theme.
Apart from the common way of changing colors using a standard color picker field, Vanguard has an additional feature where you can change all the colors at the same time using an HSL slider (Hue, Saturation, Lightness). If you are aware of this feature in apps like Photoshop, I’m sure you’ll appreciate changing the color scheme of the theme and at the same time maintaining contrast:
The other tabs allow you to customize the layout (wide or narrow), background images, fonts and the header positioning like the header height and the logo and menu top margins.