I like deep/navy blue a lot and wish more cards used it. I agree with @Wilt about Starling’s card being a bit boring, and I can’t say I’m a fan of the teal - I’d much prefer the business card blue!
Yes, the old M&S debit card is a true monstrosity! Unbelievably, it wasn’t designed by someone having a breakdown but instead by world famous designer Sir Terence Conran 