1. Click "My Site"

2. Click "Site Themes"

3. Click "Button"

4. You can see the color of the button is set to orange

5. You can see the color of the button is the same as the one presented in the Sites Builder

6. Select the color you want from the "Background color"

7. Click "Save"

8. You can see the color of the button is updated as per your changes
