We use but to link items which are the same grammatical type (coordinating conjunction). But is used to connect ideas that contrast. I am allergic to strawberries. they still haven’t sold their house in London. The phrase but not is common: The room has been painted but not in the colour that I asked for. More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.