As soon as i get it i wear it nearly all the time,apart from when in the Water temple when you must wear the Zora tunic.
When Link wears the red tunic to me it says this is Link do not mess with him or else.
The Zora Blue tunic is my favorite. It appears to be used more frequently than its Goron Red counterpart. Also, I despise the color red, and bright colors in general. I just so happen to like the blue color little more...
I like the red tunic for a couple reasons. The first being it looks awesome in OoT, and the second because it also looks awesome in A link to the past !!!
green tunic (if only for Oot)
but if for the entire series id pick zora mask (i know its not a tunic but come on ur all screaming it in ur head... lol jk)