A little more that thatThey looked like humans with oily skin. Or sometimes not oily. That's about the extent of what TOS Klingons looked like.
With these guys they were going for alien, exotic and a little threatening'
These two look you dad's friends or a Folk duo from the 60s
Koloth and Kras are just run of the mill humans in Klingon uniforms. Take away the uniform and there's nothing to make them stand out. IIRC, Phillips or someone said they had forgotten what the Klingon make up entailed when they did TTWT.