Full Idea
I make no claim to being a Locke scholar, but I suspect that the position often associated with Locke - that colours are 'in the mind' - flies in the face of Locke's considered view.
Gist of Idea
I suspect that Locke did not actually believe colours are 'in the mind'
Source
report of John Locke (Essay Conc Human Understanding (2nd Ed) [1694], 2.08.15) by John Heil - From an Ontological Point of View 17.3
Book Reference
Heil,John: 'From an Ontological Point of View' [OUP 2005], p.199
A Reaction
A glance at Locke gives the impression that he thought secondary qualities were really 'ideas', which would presumably be in the mind. Heil is hoping that Locke will agree with his own view. Further study will be required...