The example of diapers.com seems like a poor one in that its one of the few domains that I actively think about when I need to place an order -- "almost out of diapers. oh yeah, I have a coupon for diapers.com somewhere". It's one of the few domain names that has probably resulted directly in a sale to me.
Diapers.com and the the very specific ones are great but can't scale. So you sell diapers and do extremely well, can you sell baby powder? You can but at some point the name is overgrown. Color is cool and ambiguous enough
