If you don't clean it before putting in a new flavor then the wick/coil will still have some of the previous flavor on it, and it will mix in with the new flavor. I'm quite sure even with a RDA you have to replace the wick between flavors, but I may be wrong.
To be honest the only way I know of to quickly/easily switch between multiple flavors is to have multiple tanks filled with different flavors, which is why most vapers have many different heads (tanks). I myself have 4 Protank 2's, and I pretty much only vape two different flavors (I've also got two Mini Protank 2's coming in the mail).
With the Halo Triton your only real options are to:
1. Clean the tank in between flavors
2. Order more Triton tanks
3. Deal with the fact that the flavors will mix
I wouldn't recommend option 2, as the Triton tanks will become useless if you ever start using a different brand eGo battery or an APV, considering the Triton battery/tank has a different kind of threading than every other device out there (at least the ones I know about).
EDIT - I forgot to mention, that if you don't fill the Triton tank up enough so that the e-juice wicks into the coil, then when you attempt to vape on it you will just burn the wick, and that will not taste good (and it can continue to taste bad until you change the coil).