This is where you post opinions on Story (lore), Art (models, splashes, etc.), and Sound (music, sfx, VOs, etc).
You are posting in the right board. This is THE board to make your critique, so, please, don't depreciate the value of this board.
Anyways, I feel the problem with the Battle Boss line is that they're from the same game and same enemy category "Battle Boss" BB Blitz is purple. If anything, I wouldn't be surprised if the Battle Bosses are all Henchmen or top Battle Leaders of the Final Boss Veigar, and that these are the enemies that needs to be taken out before reaching him. If that's the case, them being purple makes sense since that is the Organization's color.
Afterall, You can't get upset at Team Magma for being all red or Team Aqua for being all blue. Team Battle Boss happens to have a lot of purple with blue accents.
And remember, the Arcade characters are people that got pulled into this game turned to life. As far as I'm concerned, Big Bads with matching color schemes feel like it's par for the course.