For me, green is definitely going to be the main color. Those two Llanowar Elves and the large number of decent 3-drops and fatties already available with green alone, are just begging for the deck to come out of the gates with guns blazing and just overwhelm the opponent with sheer force. Black offers quite a bit of saproling interaction to add to what green already brings. But mostly it's just more decent bodies, and there's hardly any removal here. Red likewise offers a few more early and midrange bodies and some removal. Blue can give three decently sized flyers, and a splash of white would give a fourth, but adds no additional removal. Frankly, I think, any of these three colors could complement the green. Only white is lacking except for its removal, which is good splash material.
For now, here's my R/G version. I'll try building the other two later.
I left out the Sporecrown Thallid despite its synergy with the saproling tokens, because Tetsuko has better synergy with them and powering up the fungi nullifies that. The deck still stands at 41 cards, but the last cuts already hurt a lot, and I can't decide what to take out. I left out the white splash, because there's there's more than enough stuff to play without it. Removal may seem light, but this deck has a very solid early game and should be able to generate a lot of pressure. You could throw in the Nature's Spiral to get back a Candle, and I would do that if I need more removal before adding white. The Spiral was one of my last cuts for that reason.