I don't think that everything in -or related- to the house has to be matchy-matchy, but I do believe that there should be some harmony between things.
So I started a little notebook to keep track of some things we have going around the house...
This page in particular shows all the colors we have in place right now. The center swatch is our trim and ceiling color - Decorator's White, surrounded by the colors of our living and dining room, bedroom, guest room, bathroom, and office.
One of the things that prompted me to do this was just a need to have all our paint swatches in one place, for future reference. But I'm looking at this page right now and thinking - there are no warm colors! I prefer cool tones - but one room in a warm color won't hurt... and it may balance things out a bit. Neutral camel, pear yellow/green - or even a soft raspberry pink! - might look nice in the third bedroom, so maybe I'll start thinking about that when I get back to painting this fall.