Would it add too much clutter?

I chose not to do this because the stock hazard concrete has no reverse recipe. I suppose I can add it if it's that much clutter!

Actually, I'll make reverse recipes as a second mod - I don't want them (and re-use within color groups satisfies most of the need), but I can see why one might!

Creating recipe loops can cause some confusion in the hand crafting system...you might want to make it an assembler-only recipe to avoid that.

This is a fantastic MOD

However I have the same problem, colored concrete ends up cluttering my inventory however there is a simple fix which I keep having to re-edit when this MOD is updated, could you please update the lines in the tiles.lua file and maybe the config.lua

In config.lua
line 83
UNCRAFT_ITEMS_ON_PICKUP = true

In tiles.lua
line 26
concrete.minable["result"] = TILE_MINE_RESULT[color]

replace with
if UNCRAFT_ITEMS_ON_PICKUP then
concrete.minable["result"] = "concrete"
else
concrete.minable["result"] = TILE_MINE_RESULT[color]
end

PS this will not resolve the hazard concrete issue, but it will resolve all issues in regards to the MOD's own concrete.