It wasn't just a matter of appearance. The characterization of the Season 2 Klingons was...less than inspired.
Oh, hell, they stank. Despite the popularity of "The Trouble With Tribbles" I think William Campbell made for a shitty Klingon. There was no menace or edge to him whatsoever. I can only say in his defence that the other Klingons of Season 2 were even worse.
Seriously the only good Klingons in TOS were Kor and Kang. The rest supporting them were sufficient window dressing, but Season 2's just stank.
I thought about this, and it made me consider some points:
1: The Federation and the Klingon Empire, particularly the planet Earth and the Klingons, were rival powers. The Organians preempted a war. From that point on, there were schemes and counter-schemes, but the conflicting parties were more rivals with a grudging respect for each other than "I'm out to destroy you" enemies. The rivalry seemed to take the form of only occasional ship-to-ship pitch battles; it was more like espionage. (Witness "Elaan of Troyus". The Klingon attack ship tried to provoke the Enterprise into blowing herself up before engaging in direct attack.) Even Kor, when it seemed like war was imminent, said "I respect you, Captain, but, this is war."
2: What's wrong with the Klingon Empire being a multi-racial society, with some Klingons being light-skinned, some being dark, and some having the tire-tread heads? What's wrong with that? When I saw the winter-truck-tire heads in TMP, I was only mildly impressed. (I admit, I'm probably in the minority on this point.) After all, the Empire must encompass multiple worlds, right? Maybe not all Klingons came from the same planet. I actually think the Berman & Co. idea that the Klingons became human-like as the result of a human genetic mutation virus was far cheesier than anything else in TOS or since. Berman & Co. "corrected" a "problem" that need not be remediated.
3: Witness Tuvok and
Commander Sirol. If the Vulcans and Romulans can have multiple races within a single species, why can't the Klingons?
4: William Campbell's Koloth and Michael Pataki's Korax were characters that appeared in a comical context.
The story shapes our view of Koloth and Korax. If John Colicos had appeared as Kor in place of Campbell, Kor would have been part of a comical story. (Making him a menace would never have worked... why would Kirk have allowed him shore leave if he were a threat?) Had Kor appeared on K-7, fans might see the character in a different light now. (Can you imagine Koloth's lines coming out of Kor?)
5: The
only problem I see with Tige Andrews as Kras in "Friday's Child" was that the beard with no mustache makes him look like an Amishman. That and maybe someone who gets a Capellan kligat in the chest probably isn't going to be able to cry out before dying. Other than that, Kras comes across as a credible Klingon in a story about
rival interstellar powers each trying to "win" Capella for its minerals. Under the Organian Peace Treaty, that's all they can be.