If you have children, let them pick colours, they aren't yet scared of bold choices and don't needs to explain why your hen house if some weird shade of pink or why that one rooms is a random shade of mint green. They just liked the colour and thought it would be awesome.
This kind of thing is illegible (not to mention inaccessible) for visitors. Someone comes to your city and they want to ride a train instead of driving their rental car into your downtown. Your transit requires a card. They're not comfortable with your language, they have to find a machine, and the first one doesn't work right.
They finally get a machine that works, after standing in line behind several other people. It turns out they need to buy a new special card and then load it with one of a number of confusing products.
They get your pretty card. Then they have to pay attention to where that card is at all times, and buy exactly the right number of tokens to load onto it (potentially). They can only buy tokens in a few select locations in your city, realize they have run out, and end up Ubering for the rest of their trip. Or they have to buy the timed card that expires in four days, halfway through their trip, and remember to get the next one in two days because it's not on sale yet.
We have wallets built into our phones now. Transit is a utility - it should universally take tap to pay, and more major cities are now rolling that out. Zero planning, zero extra "new and unique" objects to keep track of.
If you want a date based pass for a long visit instead of paying per trip, both Apple and Google have a way for you to buy transit passes directly from their wallet. You can always make that virtual card pretty.
Tap to pay may work if you actually use your phone as your wallet. From what I see around me, most people don't. And on this website in particular you have surely seen people advocating for cash over privacy concerns. Nor would I be confident that my card will work flawlessly in another city half a planet away before I get there. I will buy a weekly pass from a machine, though, especially if it looks cute enough that I can bring it home as souvenir.