I'm skeptical of those claims about Paley. If he hated the series so much, why did CBS even pick up the pilot?
A Google search turns up several accounts similar to this one, but if Paley wanted the series killed as soon as the ratings dipped, how did it survive for three seasons? Figures on Wikipedia indicate the show finished in 32nd, 35th, and 33rd place during its first, second, and third seasons, but the sources cited are not strong, and the information I have pegs its overall performance during 1966-67 year as a significantly lower 44th. CBS didn't have any problem cancelling Mr. Terrific, which ranked 36th that year, but somehow it renewed Lost in Space, a show William Paley supposedly despised? I don't buy it.
In January of 1966, 7.4% of television households had color sets. By November of 1967, 19.3% of television households had color sets. Since these figures were from December of 1966, the percentage of television owning households with color televisions was somewhere between these two figures. The point being, at the time those ratings were taken, something like 85-90% of television households were watching on black and white televisions. At that time, color television viewership was a niche audience of highly educated, urban, and upper income households -- in other words, Star Trek's key demographic (outside of young children).
I'm not necessarily denying the veracity of the lower figure for the second season, but I would only say that it appears in that same account that you have linked to, in which you dispute the characterization given to Paley's supposed convictions. If you find that contention suspect, why give credence to the ratings citation, unless you have found it elsewhere, as you describe it as "the information that I have". If there is another, more authoritative source for that figure, would you kindly identify it? I would also say that the narrative that is presented in that piece for the attitude of Paley and CBS brass seems substantial and cogently presented, not a skimpy set of vague and plausibly unqualified statements. Now, as I've learned here, readers of the Cushman opus might find certain aspects, if not a preponderance of it, to be similarly presented with a persuasive veneer, at least until they've been clued into the reality of its bonafides. I won't claim the ability to make the same absolute judgment about this LIS wiki, but I recognize as factual from a number of other sources, including some that convincingly quote production team members, a number of the anecdotes concerning the early development path of the series and details of its effects workings. Do you find a general factual fault in the Wiki, other than your sense of the improbability of what it states about the boardroom's attitude about the program?