Color theory in Welcome Home?

So one of the very first things I noticed when I was introduced to Welcome Home was the very limited color palette. Do you think this is just a stylistic choice keeping with the alleged late 60s/early 70s aesthetic?

Or do you think there is a potential deeper meaning? I noticed the color purple in particular is used very sparingly. Is there something important when it is used? There is also a distortion on the word purple when listing the rainbow colors in the Just So song.

Obviously, there is definite meaning behind the use of black on artifacts. Any thoughts on other potential meanings for color use?