base adds a set of color refined concrete tiles using a tint on the base refined concrete; see https://github.com/wube/factorio-data/blob/d88ce3336a31bd5b18e97eaffc796bab7afaeb0b/base/prototypes/tile/tiles.lua#L3927

It'd be great to have them supported too. Sadly, because they are created before y'all loaded, gonna have to either list them manually, or loop and match. This worked for me:

  for name, tile in pairs(data.raw["tile"]) do
    if name:find("refined%-concrete") then
      tile.variants.material_background.picture = "__Concretexture__/grid/concrete.png"
      tile.variants.material_background.hr_version.picture = "__Concretexture__/grid/hr-concrete.png"
    end
  end

note: gotta escape the - because find is a lua pattern, and patterns treat - as a meta-character. -_-

Thanks for the heads-up. I haven't played Factorio in a while, so I missed that they'd added coloured concrete to vanilla.
I'll add this fix soon.

TYVM! They don't have new recipes, just colors, in base. There are several mods that add in the recipes, which is how I came to be looking for your awesome textures on them. :)

Finally got around to adding this, as well as a new texture for refined concrete

for find, do ("string", 1, true) to perform a search that ignores special characters.