I have searched for an answer on the site, but all the questions I have found (e.g. this one) seem to be less general.
Assuming that I'm writing a cover letter to join a team working on a project called, say, 'Purple Frog', I'm not sure whether I should write
Dear Purple Frog Project Team,
...
or
Dear Purple Frog project team,
...
What are the rules that I should follow here?