I was reading this stanford entry and I can't understand how representationalism helps overcome the problem of a sensory quality without external origin that otherwise undermines belief in materialism. I quote some relevant segments from the first part of the article body:
Sensory qualities pose a serious problem for materialist theories of the mind. For where, ontologically speaking, are they located? Suppose Bertie is experiencing a green after-image as a result of seeing a red flash bulb go off; the greenness of the after-image is the quale. Actual Russellian sense-data are immaterial individuals; so the materialist cannot admit that the greenness of the after-image is a property of an actual sense-datum. Nor is it plausible to suggest that the greenness is exemplified by anything physical in the brain (if there is some green physical thing in your brain, you are probably in big trouble).... [Therefore] Bertie’s experience is not, or not entirely, physical. 
... The representational theory is usually (though not always) an attempt to resolve the foregoing dilemma compatibly with materialism. According to the theory, sensory qualities are actually intentional contents, represented properties of represented objects.
... suppose George Edward is hallucinating a similar tomato, and there is a tomato-shaped red patch in his visual field just as there is in Ludwig’s. George Edward too is representing the redness of an external, physical tomato. It is just that in his case the tomato is not real; it and its redness are nonactual intentional contents.
On the representationalist (sometimes “intentionalist”) analysis, for Bertie to experience the green after-image is for Bertie to be visually representing a green blob located at such-and-such a spot in the room. Since in reality there is no green blob in the room with Bertie, his visual experience is unveridical; after-images are illusions. The sensory quality, the greenness of the blob, is (like the blob itself) a nonactual intentional content. Of course, in cases of veridical perception, the color and the colored object are not merely intentional contents, because they actually exist, but they are still intentional objects, representata. And that is how the representationalist resolves our dilemma.
I don't see how highlighting nonactuality of a delusional visual thing fixes the problem. The experience of tomato or blob is still actual! The viewer is still experiencing a redness or a blob which is neither out there nor can be inside his brain. In other words, the illusion itself is still experienced and therefore has to be somewhere for there must be a distinction between illusion and nothingness!