What is the difference between "las faldas naranja" and "las faldas naranjas?"
Apparently both translate to "the orange skirts," but the first one uses "naranja" as a noun, and the second one uses "naranjas" as an adjective. I'm not sure how the first one is using it as a noun. Is there an error in the book? Is more context needed? Do these phrases actually mean different things?
I found this in the Fluent Forever Awesome word list for (Latin American) Spanish, but it doesn't make sense to me, especially the part "it must remain invariable:"
“Naranja” is mainly the name of a fruit (“the orange”), but it can also be used as the name of the orange color. In that case it can be used either as a noun (in which case it must remain invariable: “las faldas naranja”, “the orange skirts”), or as an adjective (in which case it takes a final -s in plural: “las faldas naranjas”, “the orange skirts”)