Having said all of that, I don’t believe Mattel would have given thought to a “second” wave of color figures. We can all emrocically agree that the first wave is all Flesh. But, based on the 1987 catalog, MUSCLE does not get the attention/space it got a year ago. Not exactly a ringing endorsement.
Well, I was actually going to say in my last post that not only do I believe there were three release waves, but I think there may have been three production waves. However, the current evidence paints two different stories:
(1) Look at the numbers of our three color groupings:

Overall, besides Flesh and Grape, I'd say their production numbers were pretty equal. Obviously, the MUSCLE DB info isn't perfect, but I think it gives us good, solid numbers.
Also, keep in mind that ALL the sculpts were made in Flesh, whereas not all the sculpts were made in the other colors. For instance, only 5 of the sculpts were made in Grape, obviously accounting for it's small numbers. Likewise with Magenta. I'm only at Part Nine of breaking down the MUSCLE Parts, but already Magenta is missing from 16 of the 24 Trees which make up the first 9 MUSCLE parts... which probably accounts for Magenta being last.
Which means, I think, that even though fewer sculpts were made in Magenta, all the Tree received an equal amount of dipping in Magenta... and therefore, I would guess that all the Trees received and equal dipping of all the colors, except for perhaps Flesh. (It remains to be seen if the fact that all the sculpts were made in Flesh is the reason for the high number of Flesh figure OR if the Trees were "dipped" in Flesh more times than they were in the other colors.
On the face of this info, it does therefore look like all the non-Flesh colors were produced at the same time, as opposed to a round of Red, Dark Blue, Purple, and then a second round of the new colors and a double dipping of Red, Dark Blue, and Purple.
(2) A bit of info that supports Flesh being produced first (despite the catalog pics), followed by the colors being produced is Satan Cross only being found in Flesh. Most (if not all) of us agree that Satan Cross is uncommon/common in Flesh... but rare or non-existent in color. If Flesh and the colors were produced at the same time, because of the abundance of Satan Cross sculpts, we'd have a colored Satan Cross.
Instead, Satan Cross must have been made in the 1st production wave of Flesh, and then "removed" when the 2nd production wave of colors was started.
The question is, were Flesh also produced in this second production wave? Because of their high numbers I think yes, but it seems odd that Mattel would continue producing Flesh figures. So then I think not...
(3) If all the colors were produced at the same time, why only package Red, Blue, and Purple with Flesh... and not the other colors?