Black is by far the hardest, but every car I have owned in the last 10 years has been black so I had to learn to get it right. The first time I did it, it took some time to get it all figured out, but totally worth the effort. Depending on the manufacturer of the car, the clear can be EXTREMELY hard. There is nothing like pulling that bad boy out of the garage and into the sun after a weekend of wash/clay/polish/seal/wax. My neighbors think I am bit odd when they stop to say hello and the car's wheels are off to be cleaned/sealed....