No alternate skins for either brother in the main stuff just their regular looks throughout. Brok keeps his signature blue skin from working without gloves while sindri stays normal colored cause of his whole clean freak thing with the gloves. Pretty interesting how their outfits change a bit as you progress, nothing major just subtle stuff that fits the story. Worth noting the blue skin thing is from all the metal work, thats actually a nice bit of lore detail they added. Their looks really match their personalities with brok being all rough and messy while sindri stays super clean and proper, makes their scenes together even funnier when you notice the contrast

The design choices really show through in how different they look its actually pretty clever storytelling without saying anything. You'll see some small changes to what theyre wearing as things move along but nothing you can customize yourself