Full Idea
It seems that functionalism can recognise no difference between my colour experiences and yours, in the case of spectrum inversion, suggesting that it fails to characterise colour experience adequately, by omitting its qualitative character.
Clarification
'Spectrum inversion' is where you and I experience colours differently, but don't realise it
Gist of Idea
Functionalism can't distinguish our experiences in spectrum inversion
Source
E.J. Lowe (Introduction to the Philosophy of Mind [2000], Ch. 3)
Book Reference
Lowe,E.J.: 'Introduction to the Philosophy of Mind' [CUP 2000], p.54
A Reaction
This is a standard objection to functionalism, but then it is an objection to most other theories as well. Even dualism just offers a mystery as to why experiences have qualities. Observing a patch of red involves about three billion brain connections.