HP-46 color consciousness?

[Duane Hess]

Hi:

I have three HP-46's with serial numbers:
1314A05176
1314A07446
1314A08789

The 1st 46 yellow function keys have a significantly lighter shade of yellow than the other two. All yellow keys on the 1st are of the same shade. All yellow keys of the other 2 are the same shade, but obviously deeper yellow. The 1st keys almost look "washed out" compared to the other 2. All 3 have the same color/intensity of red alt-symbols. Don't know how to describe it better than that.

Frivolous question. Is anyone aware of any color change in the 46's dependent on date/serial number? Or might this just be "they were lighter colored that day"?