Full Idea
According to D.M. Armstrong and others, when we perceive secondary qualities we are in fact perceiving primary qualities in a confused, indistinct or blurred way.
Gist of Idea
Armstrong suggests secondary qualities are blurred primary qualities
Source
report of David M. Armstrong (A Materialist Theory of Mind (Rev) [1968], 270-90) by Howard Robinson - Perception III.1
Book Reference
Robinson,Howard: 'Perception' [Routledge 2001], p.63
A Reaction
This is obviously an attempt to fit secondary qualities into a reductive physicalist account of the mind. Personally I favour Armstrong's project, but doubt whether this strategy is necessary. I just don't think there is anything 'primary' about redness.