so let’s say karti is leeks so it is similar to green- does that mean techeiles isn’t blue? the same ????? that says that says it is domeh to leeks says techeiles is blue so obviously the mordechai held there is is no stira. (unlike rabeinu Yonah)
The same way it is impossible to be a machlokes in metzious so too the metzious of the chachmei umos haolam have to shtim. Josephus in wars of the Jews Book 5,5 4 Antiquities of the Jews boook 3, Philo in the Life of moses 3,2 all say techeiles is blue. (and in case you don’t like translations Philo actually says techeiles is like the color of the air (horizon) see hebrew version here http://www.hebrewbooks.org/pdfpager.aspx?req=32392&st=&pgnum=98&hilite=)