The thing that in my mind most connected Disgrace to post-colonialism was the line by the "hostess" service when David Lurie calls in to find out about Soraya. They ask: "Would you like an introduction to another of our hostesses? Lots of exotics to choose from - Malaysian, Thai, Chinese, you name it." While I read this, I couldn't help but thinking about what Achebe was saying about the way Conrad perceives native Africans in Heart of Darkness.
Achebe's biggest gripe with Conrad was his writing off all Africans as savage dark people who melt into the vast jungle. They are the "other," something so clearly separate and opposite of Europe. In Disgrace, the "exotic" whores serve this colonialist purpose. They are the "other" that aren't refined, civilized women, they exist only as objects of men's pleasure. They're not just one "other" either, the pimp gives a laundry list of exotics to Lurie.
The comparison of characters that Achebe brings up is also very relevant. Achebe talks of two women described in Heart of Darkness, one white, and one black. "The difference in the attitude of the novelist to these two women is conveyed in too many direct and subfile ways to need elaboration." Coetzee too, contrasts two women much like Conrad does. Soraya, the "exotic hostess" and Melanie Isaacs, who's name is often repeated in Lurie's mind with a French inflection. In love making, Lurie describes Soraya as "entirely satisfactory," won't bore her with the details of his much more acceptable job, describes her photo as revealing the lines at the corners of her eyes, and made sure to keep his relationship with her on the down low. In fact, what sold him on Soraya was "the promise of shuttered rooms, cool sheets, stolen hours."
Melanie on the other hand prances around naked while she's changing, without the inhibitions of older, less beautiful women. Lurie describes her body as "clear, simple, in its way perfect," and finds their first tryst so pleasurable that he blanks out after climaxing. Most importantly, he lets her move into his house, knowing full well that word would quickly get out about their affair.
The way these two women, the young, bourgeois, college student, and the "exotic," whore who's age is catching up to her reveal the same thing in the character of Lurie that are revealed in Marlow. In fact, when Achebe states that "the difference in the attitude of the novelist to these two women is conveyed in too many direct and subfile ways to need elaboration," it could easily be superimposed onto a critique of Disgrace (and I think I just did that).