 There are two famous objections to functionalist theories of qualia: the Inverted Spectrum and the Absent Qualia Hypothesis. The first move in the former objection consists in claiming that you might see red when I see green and vice-versa; likewise for the other colors so that our color experiences are phenomenally inverted. This does not suffice to create trouble for the functionalist yet. For you and I are surely representationally different here: for example, you have a visual experience that represents red when I have one that represents green. And that representational difference brings with it a difference in our patterns of causal interactions with external things (and thereby a functional difference).