Full Idea
It seems obvious that Mary will learn something about the world when she is released from her black-and-white room; but then it is inescapable that her previous knowledge was incomplete; she had all the physical information, so there is more to have.
Gist of Idea
Mary learns when she sees colour, so her complete physical information had missed something
Source
Frank Jackson (Epiphenomenal Qualia [1982], §1)
Book Reference
'Mind and Cognition (2nd Edn)', ed/tr. Lycan,William [Blackwell 1999], p.442
A Reaction
This is Jackson's famous 'knowledge argument', which seems to me misconceived. Since I don't think phenomenal colours are properties of objects (Idea 5456), Mary learns more about herself, and about her means of acquiring knowledge.
Related Idea
Idea 5456 Redness is not a property as it is not mind-independent [Ellis]