Since the split from PlayerColor into the ITeam interface, the implementations of Teams are within the original plugin.
To serialise ITeams correctly, the information about which particular implementation to use needs to be passed, leading to ugly, plugin-dependant xml, so for instance:
<winner displayName="bluez">
<color class="sc.api.plugins.TestTeam">BLUE</color>
</winner>
instead of the previous
<winner color="BLUE" displayName="bluez"/>