Yeah anyone can make any color team now with the new starters. The starter 2X ATK 2X RCV combined with the greek gods 2X HP 2X ATK makes for a 2X4X2X team that can do anything. I was looking at all the various possibilities and ranked how good a mono team you could make - this team might be pretty biased as I mostly have the fire & light teams, but I think it's pretty close to true:
#1 Blue - This team really has everything, if you have Neptune (poison), Viper Orochi (Delay), Siren (Hearts), plus a couple orb changers, and some awesome subs. However, it's hella hard to assemble.
#2 Green - Parv is an heart maker, Susano active is nice, ADK has been the easiest knight to skill up so far, and some nice subs too.
#3 Dark - Pretty easy to assemble, vampire very easy to skill up, good subs in Hera & Hades (gravity), Lillith (poison) - this team can't get a 2x hp 4x atk 2x rcv, the best you can do is 1.5x hp 3x atk 3x rcv.
#4 (Maybe tied for #3?) Fire - Also pretty easy to assemble, has Enchid for delay, Shiva active, no poison or gravity though. Titan is very easy to farm & skill up, but his final evolution has NEGATIVE RCV, overall really bad RCV and no heart maker.
#5 Light - Like Dark you can't get the 2x 4x 2x team, no poison, no delay, no heart maker. You have good subs in Indra or Zeus. Easily the most difficult to level up too.
Edit: Light might be much better off just going double Zeus and blitzing all down - of course you'd have no HP / RCV modifier, I dunno.