There are two interpretations of this phrase, though other sources give only the first interpretation.
In the first interpretation, it refers to the fact that both cast-iron pots' and kettles' bottoms turn equally black when hung over a fire, and thus the pot is accusing the kettle of a fault it shares.
In the second, subtler interpretation, the pot is sooty (being placed on a fire), while the kettle is clean and shiny (being placed on coals only), and hence when the pot accuses the kettle of being black, it is the pot’s own sooty reflection that it sees: the pot accuses the kettle of a fault that only the pot has.
The translations below need to be checked and inserted above into the appropriate translation tables, removing any numbers. Numbers do not necessarily match those in definitions. See instructions at Help:How to check translations.
Translations to be checked
Albanian: I mjeri shan të përmjerrin. (The miserable reproaches the one who urinated on himself.)
Arabic: "ان كان بيتك من زجاج فلا ترم الناس بالحجارة" (If your house is of glass, don't throw rocks at others.)
Assamese: Hkhaale Hkhingik haanhe (The Shaal fish laughs at the Shingifish)
Basque: Xoxoak beleari: Ipurbeltz!. (The blackbird to the crow: Black tail!)
Bengali: Chaluni bole chhuch re tor Pichhe kano Chheda!. (The Sieve tells the needle to mind the hole in its back!)
Czech: Konvice nazývá kotlík černým (The pot called the kettle black) Hrnec hrnci káže, oba černí jako saze – Čelakovský(Pot preaches to pot, both as black as soot.)
(please verify)烏鴉笑豬黑，自己不覺得(The crow mocks the blackness of the pig, ignoring its own blackness. (an idiom from Sichuan)
(please verify)龜笑鱉無尾(The turtle makes fun of the trionychidaes that they are of short tails. (an idiom from Zhangzhou, Fujian)