Xenoblade Chronicles 3 does have a way to change each of the characters appearances to keep them looking fresh throughout the entire game. Unfortunately, the game does not disclose any appearance changes.
How to change character appearance
Before you can change any of your party members' appearances, you will need to wait till chapter two. During this time, the group will change into different clothes and start receiving new classes. Once you have reached Colony 4, you will have the ability to change everyone's appearance.
To change the appearance of a character, go into the menu by pressing the X key and select the character option. From there, scroll down and select the clothing option in the character menu. You may wear any outfit that the character has worn.
As you progress through the game, you will earn an outfit that goes with that class. You may then go into the menu and customize it for the class you like better. Just keep your outfits clean.