If their function doesn't really match with their color then it only makes sense to change it. Plus the new abilities actually do match well with the colors like white with ice and purple with poison.I really don't like the changes to white and purple Pikmin. Maybe the ice pikmin could be light blue and the spring Pikmin another color. Although I do agree that rock and purple Pikmin do have much of the same function.
Other than that, I really like the rest of it. Green Pikmin camouflaging another object is genius.
One thing I didn't clear up, is that you never permanently get Bulbmin. You can find them in a cave, and take control of them by killing the Bulbmin leader, but they can't leave the cave with you. So adding a new Pikmin that can do what the Bulbmin did is pretty cool.
As for Bulbmin, I didn't like the idea that they're not 'real' Pikmin and that they have those kind of limitations so I would rather have a new breed that does the same thing and more, and in a better way. Then you can take them anywhere and use them on almost anything.
The Bulbmin are real Pikmin. Just imagine that a bulborb ate a Pikmin seed. The Pikmin seed than grew into the bulborb's brain and took control. (Along with sprouting a leaf out of it's back) However, I also prefer your idea of the Pikmin that need to latch on to take control. It could lead to some interesting puzzles.
"A puppet that can no longer be used is mere garbage. This puppet's role has just ended..." -Majora
"A puppy can be fused with garbage. This puppy's role has just ended."