This scheme works well but it occurs to me that it would work well with 4-4-4. OTOH, 4-2-2 and 4-2-0 are very common in my line of work and they are lossy by design, so getting the color error better than 1 part in 256 is probably not of grand importance. In 4-2-2 and 4-2-0 you're going to have color error no matter what.

The major TV network I work for broadcasts in 4-2-0.