After spending some time doing research and digging through wayback pages… I now have the following information. The Navigator Pros look to have been introduced in 2002 in conjunction with similarly coloured (glitter painted) NetVista computers, manufactured by Micro Innovations for IBM (who still gets contracted by Lenovo to this day). The Navigator Pro came in two colours:
#1 Slate Blue (it appears to be the most common from what I saw)
#2 Merlot (sometimes unofficially referred to as burgundy or red)
The reason why they’re hard to find in documentation is because they seem to have been discontinued in 2003, versus the other mice which IBM had produced for a decade… and I would imagine the ‘merlot’ ones sold the poorest.
I only became aware of their existence (02/05/2015) after finding a tiny weeny picture of one on google images from a guy who was selling these by the boat load a decade ago for $15 a pop. Although (as mentioned) I should have calculated that they existed based on the colours from the corresponding NetVistas that I saw when looking for keyboards; much like the Black PS/1s and black M2 keyboards... but sometimes you don't think ahead that quickly and miss out. Oh well… at least I can reverse SOME of my lack of foresight
Like anything mass produced, as the years go by they become unobtanium and vanish away--either in recycling yards, lost in basements and who knows where else. Fortunately there was one listed on ebay new in the box which I snapped up with zero competition--because, well...
A) I'm not even sure if these are truly 'sought after' or if it’s just a ‘that’s cool’, we’ll assume the latter
B) They seem to be rather unknown
C) Why bother with an old silly mouse when Logitech has the latest 'craze' for your purchase
That's the best reasoning I can deduct, but I should cut the chatter since I am way too invested in tiny details and could go on for hours
Onto the mouse PR0N!!!!
Move over conventionally-coloured ergo mice, there's a new mouse in town.
The Navigator comes in typical striped IBM packaging from the era:
The rear of the box gives us all of the juicy 'features', some the lingo is a bit weird as optical mice weren't exclusively commonplace as they are now (while it's obvious now, in 100 years time it may not make sense to people--funny):
Check out the side piece, mmmmm that dark plum / merlot colour:
Sadly the siding is coated in a 'soft touch' clear rubber coating which decomposes turning sticky when it contact with other plastics. IBM seems to have changed this coating in 2003 or 2004 which fixed this problem (but unfortunately too late for the navigator series). This coating can be removed to regular plastic--which means it's not 'soft touch' anymore:
Different angles:
Underneath:
Closeup of the "Step-n-scroll" illumination feature:
Macro of the glitter injection plastic (it can be harder to see due to the highly textured surface):
The ‘merlot twins’ (the navigator's merlot is slightly different in colour, more 'established' and less vivid):
How does it feel? AMAZING. The Buttons are unbelievably tactile, and the scroll wheel is also 'notched' and possibly the most tactile mouse wheel I've ever used (I didn't know that was a thing). The soft rubber of the wheel is nice on the fingertips, too. The finish on the mouse is textured and feels very well too; and if the rubber coating didn't melt it would also be awesome.
In short... this is possibly the 'ultimate' tactile mouse for both feedback and 'texture' feedback if you like those sorts of things.
Regarding the technical details... how well is its travel? Unfortunately like all early optical mice (despite being 800 DPI), the software controller is configured to DELIBERATELY calculate movements slower to accommodate lower resolutions of the period. Pity. It could be 'fixed' if one wanted to do some hardware hacking or swap in some logitech guts.
Because I don't care for wheel mice and this is the only example I have, it's back in the box and going into storage. Not to mention the ‘merlot’ doesn’t really go with anything (unless you actually own a merlot glitter painted netvista case). Shout out to David Hill for designing this and choosing such intriguing colours. I'm surprised the man doesn't keep samples of these to show off in design exhibitions.
Regarding the whole name ‘merlot’, I’m not sure if the names are a David Hillism as well since they were chosen to be technical. The merlot grapes resemble the side “plum” colour more than the glitter burgundy:
https://en.wikipedia.org/wiki/Merlot
MERLOTTTTTTTT.
I’ve… just found out about another weird forgotten IBM mouse after finishing off research on the merlot navigator (which funnily enough looks a lot like one I’ve already modified with parts from three other mice). Great… now I have to spend a few more years tracking this one down. This one is not optical, however. It's like being a detective never ends just when you think you've found everything.
Thanks for reading to anyone who has gotten this far.
Family photo of my silly "collection":
Nice mice! 
