[crote]

> same for J, but that one should be more monochrome

The color is actually the main reason I dislike that design the least!

All the monochrome blobs do have a more traditional bank note feeling, but the complete lack of contrast makes them unmemorable and hard to identify. You can't trivially tell them apart at a quick glance, you have to either actively read the number or identify it by color. But the numbers aren't big enough for reading, and there are a lot of colorblind people.

Try opening them up in a photo editing tool. Blur them and desaturate them a bunch. Can you still tell them apart?