Here is a full quote that makes clear in exactly what sense he doesn't believe in qualia:

So when we look one last time at our original characterization of qualia, as ineffable, intrinsic, private, directly apprehensible properties of experience, we find that there is nothing to fill the bill. In their place are relatively or practically ineffable public properties we can refer to indirectly via reference to our private property-detectors — private only in the sense of idiosyncratic. And insofar as we wish to cling to our subjective authority about the occurrence within us of states of certain types or with certain properties, we can have some authority — not infallibility or incorrigibility, but something better than sheer guessing — but only if we restrict ourselves to relational, extrinsic properties like the power of certain internal states of ours to provoke acts of apparent re-identification. So contrary to what seems obvious at first blush, there simply are no qualia at all.

Originally in Quining Qualia, 1988, by Dennett, and quoted on Multiple-Drafts Model.

The Taboo of Subjectivity is a book by B. Alan Wallace. It appears that Dennett wrote a review for that work, but I couldn't find it online. Are you referring to that review, or to something else?

Belatedly:

• I think the reference on p. 28 is pointing out that the brain doesn't turn purple (and a purple brain wouldn't help anyway, as there are no eyes in the brain to see the purple). The remainder of the page is extending the example to further elaborate the problem of subjective experience.

• I cannot find the reference to qualia quoted in The Taboo of Subjectivity at all - p. 74 is before Dennett even defines qualia, and p. 374 does not have those exact words - only the conclusion of a thought experiment illuminating his rejection of the concept.

Thanks for the page number - I'll see if I can find it in my copy when I get home.