Well that bothers the linguist in me, typically only relevant information is included when contrasting two items. So while in general you can't assume the negat

Well that bothers the linguist in me, typically only relevant information is included when contrasting two items. So while in general you can't assume the negation of the implication, in conversation it is generally expected that if I say "I switched from X to Y because it is my favourite colour" you should be able to assume that X is not my favourite colour.