I've seen it done all sorts of ways....several shades lighter than the wall color(neutrals usually) or a bold pop of color or a sky blue of some sort.

It would be helpful to have pictures of the room and know the wall color to really give an informed answer.

I love painted ceilings... can look amazing if done properly.

We love painted ceilings other than white. We went with a creamy yellowish color in our home and it looks fabulous with any wall color and really helps the trim pop. Here is a photo of what we did.

Normally, I'd say go crazy with a colored ceiling, but you're selling so it's best to stick with neutrals like a rosy beige or pale, near-white shade of blue or peach. I helped a client pick a peach color that borders on cream to the point that most people think it is cream, but you can see the true color when it's very sunny.

Thank you all...I wish I had a picture, but don't. The trim is stained wood with high gloss - they are going to be painted with a color like Snowbound white (sherwin williams). The wall color will be either balanced beige or accessible beige. These were colors I did in my bungalow at the advice of a designer friend of mine.

Also, if we do one ceiling or two...should we carry that throughout the house?

You only need to carry the ceiling color through rooms that are connected, like great rooms or hallways. As long as there is a clear division between rooms you can have different color combos. For resale purposes, it may be best to use varying shades of cream and beige.

I saw this photo in one of the Houzz articles today and thought immediately of your ceiling question:

I love painted ceilings. I don't think you must do all rooms. If your realtor is suggesting it (and it seems the color is not over the top) I say go for it. I'm sure she wants the house to sell as much as you do.