I am mostly done wiring up the new terrain engine. It leverages the level 7 data from the 1991 Venus Magellan C1-MIDR compressed DATA at a whopping 12.6 GB!
For fun, I flew out to the landing site of the Venera 13 to get some samples of the ground color at the surface.
Without changing the base texture it is pretty darn close (sample taken from the above image and compared above the color-corrected Venera 13 panorama).
I was able to note the 0% and 100% integrals (represented by low and high values) and the peak of the curve (represented by gamma). Sending it off to Arms of Venus to see if they can suggest adjustments that can be applied on-the-fly to the base texture and/or a high-frequency detail layer that can be applied in the shader.