At present, there's no way to set a new email address on an existing Honeycomb account. We'd be happy to submit this for you as a feature request, so do let us know.
In the meantime, you can create a new Honeycomb account with your preferred email address and add it to the team, or have the team owner send an invite from the team settings page to your preferred email address.
After you have access to your team under the new email address, the team owner can remove the old account from the team.