Control the template settings from the Meridian Setting page in the dashboard, access instructions below:

The template is bundled with 4 pre-made style variants that can be easily and quickly chosen from the template configuration. There is also an option for Custom which you will choose if you do not wish to use the preset styles.
If you selected Custom in the Preset Styles option, you will now have a choice of several options to customise your sites colour scheme. Therefore, you can either manually type your desired colour into the input field or select the colour from the popup.
The names of the various selections denote the area that they apply to.