It is certainly an intriguing find and it will be interesting to see what else surfaces with these. I think of the T210 series 3 as well. Some of those fronts are very clearly orange and some very clearly red, with shades in between. It is my opinion that the intent was to make them all red, but a mistake happened and they let them through.
On the other side, you have the T206 OMSL browns that were hand cut and clearly scraps or mistakes that were caught. However, many of the T206 OMSL appear brownish when compared to the standard OMs in T206. The ones that get designated as brown are different though. The explanation of how you go from a brown to a brownish black is probably pretty simple.
Again, it's interesting and if the sample size grows it should tell us more. There is probably a simple answer on how you go from purplish to black. I would think it is possible that it was some sort of corrected mistake. They look neat, I can confirm that.
