Buttons should only be used as a call to action, and the label should make it clear what the button will lead to.
For starting a service, the button text should contain a clear call to action to "Start" the service.
Please note:
If you are using a button outside of a form, instead of ‘button’ use ‘a’ - the classes work on both and the front end result is identical.
Green buttons are intended for use as the main call to action on a page - you should never use more than one green button on a page. If your page has a few different calls to action - use blue (default).