Can I remove all blood on Monster Hunter Tri?

Solution 1:

No you can't

Monster Hunters games have a visual effect (most often red flashes) to tell you precisely when and where you hit a monster.
There are usually options to tune it down, but there's always a little effect left.

Given that it gives great information about hitting monsters or not (as they don't flinch every time you hit them), it's not hard to understand why they don't make such an option.
You should also avoid build that revolves around critical hits, as these have often bigger hit effects to differentiate them from regular hits.

I also want to add that there are never blood-related effects on players (except for Bleeding status, but wasn't here in MH Tri), so you don't have to worry about this side of your problem.

I don't personally own this specific game nor Wii, but I have experience with Monster Hunter games as a whole, plus I searched before making an answer for this game.
As a last note, you might be able to do entirely hide hit effects through some sideways solutions, like hacks, but I can't help you with that.