When it was first developed in the early 70's there was a method for selecting carb jets etc. The driving wheels would be removed, the car secured on stands, the accelerator floored and the brakes applied to pull the revs down to 2k, 3k 4k etc for a colour reading. Usually it was necessary to let the brakes cool between readings.

Sounds very methodical, mechanical and filled with analog beauty
ah the good old days!!!

Don’t know what the colortune device is but it reminds me of doing “plug chops” on my old H1 triple trying to balance the carbs and get the proper color of plug burn, then change it and do em again! Ah the good ole days

Not a H1,nice bike, but you'll get the idea:

https://www.youtube.com/watch?v=yt6m35akQrA

Interesting video especialy the Datsun one. Is it better than listening by ear?

that is pretty cool, never seen one. Kind of works the same idea a bit differently. alter the fuel/air mix to tune but this way you get an actual visual real time aid vs. look at plug color after a certain RPM rev up. Kinda neat!