Typically when we are designing a room, we paint the interior of the door the same color as the trim in the room. If you have painted all the trim white, then I would paint the door white as well. In my opinion this helps the trim, door jam, and door to all flow together.
However, if you have stained wood trim, and a paintable door, this is a different situation. You could paint it the same color as the walls, and it look just fine.
It really comes down to what you like, you are the one who lives in the home. Paint it to please yourself! (If you do not like it paint over it!!! LOL)
Hope this helps.
If there are several doors in a hallway, and the rooms are painted different colours, it looks better to paint both sides of the door white or leave them wood stained. Our rooms are different shades of the same family of tan shades and the white is a nice contrast in both hallway and bedrooms/bathroom.