Full Idea
There are good reasons for distinguishing between expressions of personal preference and evaluative expressions, as the first depend on who utters them to whom, while the second are not dependent for reason-giving force on the context of utterance.
Gist of Idea
Unlike expressions of personal preference, evaluative expressions do not depend on context
Source
Alasdair MacIntyre (After Virtue: a Study in Moral Theory [1981], Ch. 2)
Book Reference
MacIntyre,Alasdair: 'After Virtue: a Study in Moral Theory' [Duckworth 1982], p.13
A Reaction
The sceptics will simply say that in the second type of expression the speaker tries to adopt a tone of impersonal authority, but it is merely an unjustified attempt to elevate personal preferences. "Blue just IS the best colour".