Very nice. The round-edged squares for use with the pipes is very hand and needed. I also love the large pipe set up. Handy!
Also, (and here I'm just being anal) I like the layout with the grass to the left instead of on top. It is a cleaner, more orderly tileset that way, imho.
The colors do seem a bit punchy to me too. The orange red looks very "out of the tube" to use an art class term. In other words, it feels like a clean and freshly made, manufactured color rather than a dirty, poisoned surface in an industrial waste. I would add a dingy tone that contrasts with the orange/red, like an almost nasty green/brown. This would give you a tarnished looked that would nicely contrast with the radioactive bright colors. Nothing brings out a bright color like a dingy contrasting one.
The red bumps on these blocks remind me of legos. I love legos.
Red stuff is waste not plant? I think it looks a little too much like plant then. I never would have seen it as anything other than a plant. Again, I think it is partially due to looking too vibrant to be a waste product.
Your idea for how you will use this sounds really cool. Ever read Battle Angel Alita?