MS2 likes to paint, weld, and score the chassis of her mecha form (it is a separate body which she can remote control for short periods of time). She wants to get a tattoo but can’t decide on anything, so the fact that she can always start over with a fresh canvas like this is very appealing. She probably puts stickers on it too. And then when it’s time to take the thing out on a mission it’s still covered in whatever since she doesn't repaint it to its base colors until there isn't any more room to draw on it.