The Crab with the Golden Claws was drawn (with several interruptions) during WWII, and was published in a black & white volume in 1941. With the color edition appearing in 1943, it was among the earliest of the editions to be reprinted. It makes sense that this story would have fewer difference between the B&W and color editions, a comparison of the two shows some interesting differences.
It's tough to compare different editions, since it seems that tweaks are ongoing. Other than the obvious change of translating the story from French into the local language (English, in my case), other changes that have been made are revised fonts, cropping of panels, and the addition of the hors-texte (full page wordless panels). For this article I compared a reprint of the 1941 "Le Crabe Aux Pinces D'Or" with a mid-80's version of the color edition from Metheun / Magnet.
According to this article on Wikipedia, most of the changes made to the color edition were later, at the request of the American publisher:
"In the 1960s, the book was published in America with a number of changes. In the original, the sailor Tintin leaves bound and gagged in Captain Haddock's cabin, and the man who beats Haddock in the cellar, are black Africans. These were changed in the 1960s to a white sailor and an Arab due to objections by American publishers of having blacks and whites mixing together.  However, Haddock still refers to the man who beat him as a "Negro" in the English version. Also at the request of the Americans, scenes of Haddock drinking directly from the bottles of whisky on the lifeboat and the plane were taken out."In an interview, Hergé sarcastically stated that these moves were "justified" because "Everyone knows that Americans never drink whisky(!)" and "that there are no blacks in America(!)".
So, first let's look at the characters who are no longer black in the color editions. When Capt. Haddock is captured by the smugglers he's tied up and beaten by one of the crew members. Later the Captain escapes, and chases his tormentor down the street yelling "You have to arrest that Negro!" In the color edition the man has been change to look more like a Spanish sailor, but the text still refers to him as a Negro.
Another character named Jumbo is also changed from black to pink. The name "Jumbo" is a variation on a Swahili word that means "hello" or "chief." Also, the father from "Little Black Sambo" is named "Black Jumbo", so it seems that Herge meant for the character to be black. The Tintinologist site has a color version of the black character from 1958, which reinforces the suggestion that the change was made for American markets.
In the B&W edition, at the beginning of the book, when Tintin sees the Thom(p)sons on the street, it's at the "Cafe du Sport." Later, in Morocco, the Captain waits for Tintin at the "Cafe du Port." In the color version both signs have been erased. As a side note, I like the way the letters are shown backward, as if seen through the sign via the sun.
Another translation-related change is where "Au Secours" has been erased, but still shows over the window frame.
A more artistic revision is evident in the scene where Tintin and the Captain start out across the desert after their plane wreck. In the original edition the handkerchiefs suddenly appear on the heads of Tintin and the Captain between the frames, as they also rapidly lose their coats. The revised edition has them still in their coats, sans hats. Then, the larger desert panel gives the space to suggest some time has passed, and shows them coat-less and wearing their handkerchiefs.
Another change requested by the American publisher is to omit panels where Captain Haddock has his lips to the whiskey bottle. The "Golden Claws" is the first time Tintin meets the Captain, and he's introduced as a drunken wretch whose alcoholic life has led to the point where he's working for smugglers. So, it's especially odd to include all the other pages where the Captain is stumbling and rambling from intoxication, yet to decided to hide two simple panels of him actually drinking from a bottle. Nevertheless, the change was made. In my opinion the edit neither helps nor hinders the story.
The final change is the one that has the most impact on the story: two sequences have been swapped for dramatic effect. The B&W version starts with Tintin in disguise, on the trail of Mr. Allan, to see if he can find where the first mate is holding Captain Haddock. Then, it has the humorous sequence where the Thom(p)sons accidentally stumble into a mosque. In my opinion the color version works much better, showing the Thompson's antics for comedic effect, and then heightening the tension for the final acts of the story with a furtive chase through the alleys of the port city.
So, what does it all mean?
Well, for one thing it tells me that editors aren't omniscient. It's significant that, while the American publishers were concerned about racial issues, they weren't concerned enough to pay attention to the character names, or how the characters are referred to in the story. Also, if they meant to sanitize the story to avoid offending people with racial stereotypes, why weren't other questionable caricatures, such as the Japanese agent, and the Arab shopkeeper altered?
I'd like to thank the Tintinologist.com site, who provided a great chart of the publication dates of the Tintin library.
Read Tintin in Black & White Part 1 - The Cigars of the Pharaoh. Also check out my review of Tintin in the Land of the Soviets.