Dollar coins are an improvement over bills in every possible way.
The US Mint has been manufacturing dollar coins for years now and they CANNOT get rid of them. They don't work in circulation and are just sitting in a vault, costing money to store. They have literally been a massive waste of taxpayer money. Nobody uses them. Nobody wants them. If you pay with a dollar coin people roll their eyes at you like you're some sort of asshole.
There used to be a good scam, with dollar coins though. See, you could actually buy coins from the Mint. Buying money. You just paid shipping and handling.
So what was the scam?
Well people would buy coins with a credit card. Sky miles. Reward points. You name it. You paid $500 for $500 in coins, got 500 reward points, and soon you'd be flying around the world.
The only problem? You'd have to find a way to spend the dollar coins! And it was a pain. Nobody wanted them. People would end up buying money from the Mint and then just bringing it back to their bank who would send it back to the Mint and it'd sit until someone else felt like scamming.
Now I know you're just being ridiculous. US paper money is terrible, precisely because it's all green.
The whole world has been going green over our money for the last 50 years. Green is money. Money is green.