Why is Everyone Else's Money Prettier Than Ours???

I'm just saying---our money is kind of blah in comparison to other countries, don't you think??? Our bills are all the same size and green....not that I am not a fan of green but I think it is nice to mix it up a bit! Doesn't it make sense to have graduated sizes and different colors for easier identification??? I just think it makes more sense. I think I need to do some research on why our money looks like it does---I am sure there was a reason to design it the way it is but hey----let's liven things up a bit!!! Thoughts???