Full Idea
Primary qualities and secondary qualities are often distinguished on the grounds that secondaries are restricted to one sensory modality, but primaries can appear in more.
Clarification
A 'modality' is a way of doing it, such as sight or hearing
Gist of Idea
Secondary qualities have one sensory mode, but primary qualities can have more
Source
Howard Robinson (Perception [1994], VIII.7)
Book Reference
Robinson,Howard: 'Perception' [Routledge 2001], p.207
A Reaction
This distinction seems to me to be accurate and important. It is not just that the two types are phenomenally different - it is that the best explanation is that the secondaries depend on their one sense, but the primaries are independent.