Is not the canonical way to say "purple" Doq 'ej SuD, in that order? (http://klingonska.org/canon/2011-09-30-tnk.txt)? Is it established that the order can be switched?
If not, then perhaps SuD 'ej Doq would be how to say "blue and red", as in the Haitian flag (as James suggests).
It could be that Doq 'ej SuD is lexicalized for purple, or it could be that it's simply a description and can be reversed. We don't know. I'd keep it safe and switch it to Doq 'ej SuD, just in case.
I don't think so. I believe je is used to connect nouns (as in torgh mara je, "Torg and Mara" ), not verbs/adjectives.