Is 'the color purple' a syntactically sound sentence? Or would 'the purple color' be a more standard version. I'm basing this on the fact that adjective-noun order seems a more acceptable syntax.
It depends on what you want to say. Both are perfectly acceptable.
Saying "the color purple" you refer to purple which in this case is a noun. Purple is a color.
On the other hand, "the purple color", you're referring to the color which is purple and in this case purple plays the role of the adjective.