Thanks for the information!
It sounds like you're experiencing racket-hash-lang-mode not highlighting buffer with font-lock · Issue #642 · greghendershott/racket-mode · GitHub.
Could you maybe please chime in there?
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They mentioned that indent does work for them. It would be interesting to know for you, too.
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If you move someplace you expect color -- say within a string value -- and press
C-u C-x =it will open a buffer with properties about the char at point. If you could copy that for me to see, that would be useful. 
Thank you!!