I have a set of Uncle Henry slipjoints that I refer to as "blackies". These knives, an 897UH, 834UH, and 807UH have nearly black coco colored scales. Only when compared closely with regular appearing production Uncle Henrys do you see what is going on with them. They are not flushed with the bolsters, pins, and shields. Looking closer, you can see the higher ridges of the "stag" have not been smoothed down to reveal the cream base layer leaving the coco color in the low areas. What I am seeing is the top accent color before buffing. Maybe this is what you are describing on your knife, only with the sawcut delrin.
It is interesting to see long production knives like the 8OT from various times. Some of the earlier ones are very light brown on top (some may be faded too), and some have a nearly transluscent base layer. Some had a tan or "buckskin" base layer instead of the cream. The top layers seem to have been changed in color pigment several times as well. Given the evolution in high temp injection molded plastics in just the past ten years, I am not surprised.
Codger