Looks can be deceiving, regarding types. It's possible that they're meant to look like Fire/Water/Grass, but are, for instance, all Normal types. They do all look fairly "normal" as far as pokemon go - they look mostly like the animals they're based on, rather than being relatively fanciful. The fire type doesn't have fire coming off its body or otherwise look particularly fiery. The grass type doesn't even look like it's made of grass, just like it's wearing a grass-shaped hoodie. The water type looks like a blue frog. I'm not saying that they're not Fire/Water/Grass - that's the most likely case. But it's not yet confirmed.

As for Chikorita, I assume you're asking because I added "or amphibian". That was mostly just a catch to make sure that anyone who disagreed about one of them being a reptile (which is likely - that they're all reptiles, that is) doesn't get to complain. Mostly, Venusaur and Meganium are the ones that might not be 100% reptile, as they are a little more fanciful in design than the others. And yes, most fire starters are orange... with red. Orange and yellow, with no sign of flames, smoke, or other signs of fire, could just as easily be pure Psychic (think of the Abra line, yellow with some brown), for instance. And perhaps frogs are associated differently by region. In Australia, Green Tree Frogs are quite common. Cane Toads are even more common. Few really associate them with water - indeed, cane toads are usually found hiding from the rain - they live in burrows, and when it rains, their burrows get wet and they make their way out of them, often onto verandahs of houses and to other such dry locations.

And you seem to be calling Flareon a fox because it's red, has a dog-like face, and a fuzzy tail. This is somewhat of a stretch, in my opinion. Indeed, to me, it's closer to a hare than a fox (based on its ears, legs, the fluffy tail, and the relatively short face), although I stand by my decision to call it a dog.