Whatever the case, I hope the grass starter is not green, the water starter not blue, and the fire starter not red. C'mon! Do they always have to be the same color? Do they?
It doesn't make much sense! Let's have something different, something new, something inspiring!
Here's my interesting triad.
Grass/Electric Corn! Yea, corn! Its cobs of fun, and it has no legs or arms. Its also got brown leafy arms to surround its yellow, kernelly face. The reason for grass/electric is so you're assured to beat your rivaling water type assuredly. Can't go wrong there.
Water/Ghost (starting stage two) water elemental. Some sort of Undine or Sea Nymph type beast who's ghostliness comes from its mystical nature. A very fun thing to see as a male though. Also very fun to connect the ghost breeding group with the waters, passing moves like Night shade and Willowisp to water creatures. Imagine Tentacruel with Night Shade, or Gengar with Hydro Pump, or even Gardevoir with Hydro Pump. Chain Night Shade all the way to Chinchou if you so please for fun times. It's main color would be purple, closer to red than blue though.
Fire/Bug army ant. Actually, in stage one, it's type would just be bug, but at evolution, it will grow into type two of fire. We need a few good bug types, and a starter is certainly a way to get something to be assured to have good stats all around. Unlike most starters, it would have two abilities, with ability two being Swarm. Basically, a Swarmed Singal Beam can hurt bigtime, and having Fireblast on hand for Skarmories is certainly not a bad thing, now is it? Bug type two adds an edge, (or rather, it's type one, but what's the actual difference?) It resists its starter rival corn with an extra layer of grass resistance, and an extra way to STAB the enemy super effectively. It might even have access to Giga Drain, the way most bugs do, even if the typings disuade its usage. Bug is also resisted by its ghostly foe. A true connectivity is formed therefore in that both STABs are resisted. Now, that doesn't unfortunately stop the Bites and Crunches that all ants are known for. Its color would be a bright sea green.
All in all, a different, yet IMO, a very fun triad. With their type coverages, and probably varied movepools, you can have tons of fun with your starter!