Exactly my thought! It's very neat but I wouldn't feel comfortable hiting the send button without double checking the actual letter address. A color bit darker or a bit lighter and your coins are gone for good!
Even when I send by scanning a QR code, I double check the actual address by glancing over it!
Just check the first and last few digits and letters of the address. You should be able to quickly verify if it is correct or not.
Maybe for small transactions it wouldn't matter too much, but larger ones definately.
I see a market coming btw with people hosting slicht color changed images like that to lure people in to send funds to them.