Almost all the meforshim define argaman as red not purple. (Perhaps one could argue that they didn’t have a good Hebrew word for purple.)
However, Philo and Josephus who saw the argaman of the Bais Hamikdash, describe it as purple.
If it is in fact purple, then it almost definitely comes from Murex snails. Even if it’s red it could come from Murex snails.
Also, this is all assuming that Techeiles is blue. But the Chavos Yair says that Techeiles is purple, and the Yerushalmi and several midrashim, imply that Techeiles is green.