Thought I’d give the card design a go.
Whilst not a designer but a marketer I think the hot coral has to stay just like Monzo say. I love everything black and would jump at having an all black card, however this is Monzo’s brand.
The design isn’t anything ground breaking, it’s more of an update of the current version. Trying to achieve the hot coral is a guessing game as Monzo don’t have any official brand guidelines. Also as nice as a white MasterCard logo would be it’s not possible based on their guidelines.
I also stuck with the horizontal version as I don’t think the vertical version adds any value apart from looking different and more like a hotel key card. Plus I have a card holder as my wallet, so “monzo” sticks out nicely and is 1. a good conversation starter and 2. easy way for me to find which card I need.
Personally I think the Monzo 
should be on the card to help enforce the brand more. And should be changed similar to the app depending on what status/account you have.
But yeah, here is the design and my thoughts.
