It depends on how adventurous you are..if you are gonna put on a non transparent case then any color doesn't matter. If you are yolo like me, I don't use any case for my honor v3 and vivo x200 ultra that's why I chose brown and red for the unique colorways.
I tend to get one of those translucent cases for my slab phones as a 'compromise'
for foldables I think I can't afford to go naked with it... can't imagine the heartbreak if it suffers any chips or cracks. wonder if there's such thing as translucent case for the foldable, haven't come across any.
exciting to await the phone coming to SG.