This is largely cultural and language sensitive. I took the test as a french native speaker and got a green-blue boundary greener than the average population with the commentary "For you, turquoise is blue". Indeed it is. It is called bleu turquoise in french.
Both likely come from (middle) dutch bakboord (the side of your back) facing the stierboord (the side with the steering oar) . Stierboord became estribord then tribord. Its more explicit in modern german and dutch.