AFAIK, it goes like this:
Hurst/Sola Sound Tonebender MkI - 1965-66 (folded steel housing, gold/dark grey, three transistors)
Sola Sound Tone Bender - 1966 (cast housing, silver, two OC75 transistors)
Sola Sound MkII Pro 1966-68 (cast housing, silver, three OC75 or OC81D transistors)
Vox MkII Pro 1967-68
Sola Sound MkIII 1968-69? (stamped housing, very rare)
Vox MkIII 1969-74 (Ge), 1975 (Si Jumbo TB circuit, reversed input & output)
Sola Sound MkIV 1970-71 (first to have the stamped Colorsound housing, in silver, orange or yellow)
Sola Sound Tone Bender 1971 (yellow, first to have the "Batman" graphics)
Sola Sound Tone Bender 1972-74 (silver, Ge), 1975 (Si, Jumbo TB circuit, reversed input & output)
There were also versions of the MkII made for Marshall (Supa Fuzz) and Rotosound (Fuzz), as well as some Vox MkIII/Rotosound/Marshall oddballs, with various silicon and germanium Veroboard circuits which didn't make it into volume production.
Up to '68/'69, these all have Veroboard circuits. The first 3-knob pedals,from '69/'70, had an "upside down" PCB, with the earliest examples having four transistors - one used as the diode.
All the above were made in England by Sola Sound. Sola Sound was registered as a company in November 1964 and Colorsound was not a separate company, it was a brand name used by Sola Sound and wasn't applied to Tone Benders until 1974 (Supa Tonebender).
The two transistor Vox Tone Bender sold in the USA was made in Italy by EME (who made the Vox wahs), and later Jen, but these were sourced independently by Thomas Organ and had nothing to do with Sola Sound
, other than lifting the name and case design. The only Vox Tone Benders sold in England at this time were the MkII Pros made by Sola Sound.
Here's a line up of three knobbers, from left: '70 Vox MkIII, '70 Park, '70 MkIV, '71 yellow TB, '74 silver TB. All these were dated from the pots.