We don't have synonyms for half-blue yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are half blue.
(n) :
Alternative form of half blue. [(education, athletics) Sporting colors that are awarded by a university or other institution for sporting achievement at a lower level, or in a more minor sport, than that required to receive a full blue, especially and originally at Oxford and Cambridge University in England.]
(n) :
Alternative form of half blue. [(education, athletics) Sporting colors that are awarded by a university or other institution for sporting achievement at a lower level, or in a more minor sport, than that required to receive a full blue, especially and originally at Oxford and Cambridge University in England.]