I have the picture molding painted the wall color in my 1899 Victorian double. (The house wouldn't have had crown molding when it was built, and I therefore didn't add it during an extension recent (and still on-going!) renovation, so I can't help with that.) My 10-inch base and all other trim in the house is painted white, and my walls are a sandy beige, or a cream-with-a-little-coffee-added color. I think you can handle it however you want and either way would be appropriate. As someone else pointed out, painting trim the same color as its adjacent surfaces (crown the same as ceiling color, or picture molding the same as wall color) will make it "disappear" a bit. If it's something you'd rather highlight, paint it the trim color for the contrast.

acountryfarm, is that glossy paint on your ceilings, or a semigloss? DH is into flat flat flat, yet I think the glossy finish can yield some interesting effects. We used our ceilings to tie the open rooms together. So the wall color in the DR went on the ceiling in the library and the walls in the library went on the ceiling in the foyer. The DR ceiling is in the blue, a project waiting...when I get some scaffolding, my plan is to paint it like a sunset sky. What's really interesting is, because the light is so different, the paint on the wall in the DR looks completely different than it does on the ceiling. Our carpenter refused to believe me, until he took an actual swatch and held it up against each to see that they matched. I also used darker ceiling colors to bring the ceilings down in smaller rooms. So the tray in the study went a dark taupe to offset the high ceiling in a smaller room. I did the same in the master bath as it too is smaller yet tall.

HGTV often implies that crown molding needs to "pop", but I think you may need to decide what's more important to you: showing off the molding, or making your ceilings appear as high as possible. Low contrast, letting the moldings blend with the wall, will make the ceilings appear somewhat higher. Painting the molding in a contrast will shorten the ceilings by however deep the molding is (a few inches?), and draws attention to your 8' ceilings. I have 7.5' ceilings at the sides of my living room & kitchen that peak to 8' in the center. I painted the molding in the same matte color I used on the wall, and I love it. The molding doesn't disappear, it still adds architectural interest, a more finished feel to the room, but the ceilings appear much higher than they did when the molding was dark. Using the same color in a higher sheen could be an option, too, since it would allow the molding to blend slightly with the wall but make it show up more than if the sheen were as low as the wall. Martha Stewart has a lot of trim matching walls in her homes, but possibly with a higher sheen. Here is a link that might be useful: Martha Stewart's Homes

why not do the walls, crown and ceiling in a bright white? Decorators white, super white, are all bright whites. Then for the baseboard and window trim, do a soft gray, or sage or blue or even charcoal. they did the crown w/these two