I have the blue and it looks gorgeous - in a case. I’m actually not a huge fan of how the blue treated titanium looks once it’s all greesy with skin oils. I actually hated it outside of a case. The natural titanium probably looks the best overall.

Blue = iMessage. If it’s green, it was SMS, soon it will be RCS. When you don’t have a strong internet connection, depending on your settings, messages will revert to SMS. When you see the green, even if it’s to another iPhone, it is NOT iMessage and is NOT secure (sms is sent plain text)

Darker blue / green message bubbles.

Settings->accessibility->per app settings.

Add Messages, then turn Increased Contrast ON.