Sign Customiser allows a merchant to easily set the colors of almost all components shown on the customer-facing app, including buttons, labels, backgrounds, etc. This allows a merchant to change the colour using no code through the admin and without having to use CSS.
To change the colors for a particular component, do the following
Navigate to the admin of Sign Customiser on your store.
Click on "Customisers" in the home menu
Click on the customiser you wish to edit
Click on "Theme Colors" in the lefthand side menu
Click on an available color and use RGB selector to choose your desired color for that element.
Click on save at the bottom of the form.