Thank you guys! It was fun to get them done and all lined up in a visual timeline:
Left to right:
Season 3 (same as Season 1, but no extra button)
Season 4-5 (or "super tape" as I've come to think of it)
Deep Space Nine (before the long grip version)
I didn't build a specific Pulaski / Season 2 hypo as I'm still not sure if the color is actually different from the Season 1/3 version, or it's just the film color throwing it off.
I chose my TNG paint colors by comparison of the various hypos next to other medical props. Since the other items like the modular tools and sample extractor changed very little over the seasons, it was possible to see at least in a rough way how the hypo colors related to each other through them. The screencap below from season 3 is a good example of how baffling it is... look at all the different grays!
The process was by no means exact. I chose what felt closest in relation to each other and the other medical props, while still looking good as a set. I did limit myself to only the enamel greys available through Krylon, for sanity's sake.
Here are some closeups of the hypos, along with the paint colors used:
Season 1 & 3
Neck and body: Pewter Gray
Grips and head: Classic Gray
Neck ring: Leather Brown
S1 extra button: dark brown vinyl decal
Season 4-5 and 5-6-7
Body, neck, 5-6-7 head: Pewter Gray
Grips and 4-5 head: Stone Gray
Buttons and neck ring: Black (also can have medium brown buttons, maybe "Brown Boots"?)
Season 4-5 "Super Tape"
Head, body, grips, button: Stone Gray
Neck: White (very slightly off-white... I think it was white primer or Dover White)
Neck ring: Leather Brown (a red-brown primer might be more accurate; I chose the Leather Brown to match the Season 1-3 neck)
This variation needed the smaller button removed, and its shape modified:
I added a styrene plate on the bottom face and then sanded the face where the nozzle goes to sharpen up the triangular profile to match the auction photo. The styrene provided the square profile around the base as on the original where white tape goes - otherwise the tape would have wrinkled as it wrapped around, and removing material to make that shape would have made the head too small for the neck.
DS9 and Voyager
Lighter silver: Dupli-color Med Marblehead Met BGM0478
Darker silver (DS9): Dupli-color Gunmetal Met BGM0344
Blue: Dupli-color Medium Maui Blue Met BGM0423
Buttons: Black and Ivory