Global Styles parameters allow to specify some styles for the current template version. The template will use specified setting for all available template versions including "Custom Style" also. This way you can overwrite few default template styles.
None of the provided color version meets your expectations? Why don't you create your own template style?
Under "Custom Styles" tab you will find many color seettings to configure and this way compose your own template version!
What does it mean?
If you like the themplate design but all available template color versions are not suitable for your business, it's the styles area that you need to use to create the template color version that you like best!