Color of paint, or stain for that matter is a personal preference. Just be aware that you will probably pay a lot more for stained crown molding because it will have to be made from top grade lumber... assuming you are talking about a true transparent stain. Much of the primed and painted molding used today is "finger jointed" if it is not made of some sort of fiber board. This, when compared to high quality wood, is much less expensive. Also, with the imperfections in drywall, caulk is often used to fill in gaps when using painted molding. Caulk just won't work when staining your trim. You will need a master carpenter to work long and hard to get everything to fit just right... again increasing your cost. If you want to put the money into it though, it may be beautiful.
While you are at it, why not add some wainscoting and bookshelves? Then you could really have some fun trying to learn if Miss Scarlet really did do it in the Library with the candle stick... or was it Colonel Mustard in the Study with the revolver?
Seriously... it could look great! Again, it's personal preference. Here is a link to a Google Image Search for Stained Crown Molding... see for yourself how you like the look:
http://images.google.com/images?hl=e...-8&sa=N&tab=wi
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