You can click on the Visual Identity tab on the left menu to access the Visual Identity page.
How to Edit the Primary Color - Colors tab
You can edit the primary colour by moving the circle along the colour line. An example will be displayed in the square on the left. Different example of components will also be displayed below the colour selector (Example buttons, Example check box, Example switch).
By clicking the Save button, the success tooltip will appear on the top and your primary colour will be changed.