It's ludicrously easy to make arrows pink or whatever. I did it some time ago for shit and giggles. I guess it does help to make especially those hard to notice weapons pink and pink projectiles definitely help finding them. I just can't be arsed to do such stuff since that shit looks ugly as fuck.
But indeed, while it's definitely a form of cheating it's not a huge deal and forbidding it would forbid all "legit" custom textures, which may or may not be a shame: I don't use any . Anyway, regardless of the poll I bet nothing will happen.
Being able to make bushes and whatever invisible is a huge shame, but if someone wants to play with a pink spear and shoot pink arrows, I don't care. If the devs can be arsed to do something to the mod, rather add a new gameplay mode or something.