True, true, but trust me, I've back in the old days be programming a lot of small tools to work with this, as I've been a games coder since the 1980s. So I do know what I'm talking about, as color limits have been haunting me a lot back then. For starters, in a non-digital thing... In space colors can sometimes changed based to the position of the sun and how light breaks in the planets atmosphere and sometimes even some processes taking place in the surface.
Next, I remember the first graphics card and it could only produce FOUR colors on one screen. And then you could either have white-magenta-cyan-black or yellow-green-red-black, and that was all. The successor could produce 16 colors, and before we moved to Windows 95 256 was the limit.
Now for some kind of 'personal challenge' I've been recently working with color reduction routines. As soon as you reduce colors, inevitably some colors change drastically. Some pictures hardly show any difference and some are hardly recognizable even with the most expensive reduction routines. Then also note that the old picture was hardly able to get the proper shape of the dwarf. Then how can you possibly expect it can come with the fine tuned color settings (even more since computers couldn't take it at the time) to be completely right? All it got was a few global rays, and the computer had to "guess" a little (as far as you can speak of 'guessing' in coding algorithms).
Then out of the computer view and comparing cameras to human eyes (the mechanics of the human eye and a camera is the same). The less you can see stuff, the harder it also will be to tell the color. Of course, part of that is your brain doing (your brain deems shapes more important than colors. This is also why everybody gets colorblind when the light is below a certain level), but it's also the lack of properly colored light. In perspective with Pluto I must note that light of each colors travels at its own speed and is more easily stopped than others and blah blah blah. A camera can catch certain colors easier than others, and especially on that distance this gets harder and given the lower technology at the time.
So from physical aspect, biological aspect and also from coding aspect it's all possible. And I also wonder how hold the 'blocky' picture of Pluto is. Pluto was discovered in 1930. That's 90 years ago. Computers didn't exist back then, and color pictures were not common then either. I deem it possible a BlackWhite cam was used.
