Zig Zagged: Bob wears a white shirt to one battle and gets injured badly. At the next one, however, he escapes unscathed.
Nobody wears a white shirt to the fight.
Or someone does, but doesn't die or lose very much blood.
Enforced: The fight scene didn't look violent enough for the series' target demographic, so they made the characters' shirt white to help the blood stand out more.
Lampshaded: "...Ouch, the white shirt makes the blood look even worse."
Invoked: Knowing that he will probably die in battle, Bob wears a white shirt to make his death dramatic-seeming and spectacular as he leads the suicidal charge against the enemy.
Defied: Not wanting to stick out and thus be easily targeted by the enemy, Bob refuses to wear white to the battle.
Discussed: "Hmm, what'll we wear to the fight?" "Well, the ones wearing white always seem to end up in danger..."
Conversed: "Oh, you know that guy is going to die. No one wears a white shirt into battle and have it remain white at the end."
Deconstructed: Bob's injuries also sever nerves and he's unable to feel the pain. An onlooker sees the blood and he's rushed to the emergency room. Had he worn red, he might not have made a full recovery.
...You might want to wear green instead- you might get killed on the way back to White Shirt of Death!