What I care about for my allies:
1) Actively Playing
2) Doesn't nuke my raid bosses consistently
3) Sufficient Power to kill, Overkill (including Rainbows) not required
4) Speed
5) Toad Lily/Edelweiss combo is a plus but not required

I have 4 rainbows myself (two were guaranteed though) and over half the rest are golds, so idc about whether my helpers have rainbows as long as they're strong enough to contribute and are active players. Like the list says, high speed is great (easy to build teams with lower speed if the maps require that) and Toad Lily/Edelweiss is nice for maps like 12-3/12-5 farming. I honestly couldn't care less if the helper team has a rainbow, I'm strong enough now that I don't NEED a OP helper team.