At Great Adventure (Six Flags in New Jersey) on the indoor rides I’ve been on they paint the devices to make them blend in, and it usually looks pretty bad. I saw a bunch of Wheelock MTWP (Newer Version with horizontal strobe) that were painted with brown and grey paint to make them blend into the fake-rock wall, and honestly I think it made them stand out way more. They had a few sprinklers, but I don’t remember any smokes or heat detectors.