I've not found much difference in the plushness of mf towels between the colors as much as between the different brands. Early this year, Don2001 pointed out that the neatitems towels varied a little. He posted that the mint green was plusher. I went back and looked closer and could feel and see some difference, but not much (I do have all the colors.) I'm comfortable using any of the colors, not just the mint, on my black paint. There was much more difference when comparing quality mf towels with the lower quailty ones. It seems that most of us agree that the Miracle Towels and the Neatitems Towels are the best in terms of quality, plushness and value.
I think rad21 is right, just a little variation in manufacturing from batch to batch.