These words are a special type of compound nouns, but they're more than just a different way to affix an adjective to a noun. They are new words with their own life, and they can have acquired meanings that go beyond just the noun plus the adjective, or a different meaning altogether.
E.g., a Blaulicht isn't just any blue light that shines blue. It's exclusively used for the flashing light on police, ambulance, and fire department cars.
Kleintier has a (more or less) fixed definition in veterinary medicine, and a different one in tenancy law.
Rotfront was a communist paramilitary group in the 1920s and today is sometimes used as a derogatory term for far-left activists.
Kleingruppe is often used with a fixed definition for the context. For example, a railroad company might have special ticket prices for Kleingruppen, and then Kleingruppe has a fixed definition in their terms and conditions like "a group between 3 and 10 people plus up to 10 children below 13 years". So if you use Kleingruppe when buying a ticket, it will be understood to have that definition.
Reinform is basically a chemical term (pure form of a substance in contrast to a mixture) that can also be used in a figurative sense ("Der Artikel ist marxistische Theorie in Reinform.").
So while the literal meaning can in many cases be a guidance in understanding a compound word, in other cases the whole isn't just the sum of its parts. Trying to build new words by concatenating an adjective and a noun won't work in most cases either.