Well, I am no expert on Reno chips but I'll give my opinion.

Up until 4 or 5 years ago only the grey chip was known. I recall asking others what the chip was used for as the grey was a fairly common chip but no others were known.

Again, details are fuzzy but a chip distributor (in Vegas or Reno) went out of business. Among the chips bought were three sets of Monte Carlo roulettes. All three sets were drilled. I assume the entire order of chips were sent to this distributor. He drilled three sets and kept them in case of reorders.

So, up until these 6 colors were found the grey was a mystery chip. We now know it was a part of a 7 color set

Now the experts can correct all my assumptions.