Consider other elements in the bedroom. White wainscoting will work in almost any bedroom, but perhaps you can match its color with a color in the comforter, window treatments or painted furniture.
Decide whether to match it to the painted trim. Wainscot is typically painted to match the trim, especially trim that abuts the wainscoting, such as baseboards, windows and door jambs. When painting wainscot a deep color, paint the baseboard, chair rail and trim white or a very light, neutral color.
Make the walls look taller by painting the wainscot and the walls the same color, but in different shades. Painting the upper walls a velvety flat and the wainscoting a semi-gloss is practical because the lower walls typically get more abuse, and provides just enough contrast to highlight the wainscot paneling without looking too uniform.
Provide weight to the room by painting the wainscot a dark color to contrast with lighter walls and ceilings. Pick a deep color to match another decorative element in the room, then paint the walls and ceilings in a much lighter shade of the same color. Contrast the dark wainscot panels with a crisp white baseboard, chair rail and other wood trim in the room for a very traditional look.
Create a cozier, more intimate feel by visually bringing down the ceiling to match the wainscot. Use a mid-range neutral, such as a deep taupe or sage green, on both the wainscot and the ceiling, and choose a lighter, creamy shade for the upper walls. Think of the ceiling as a fifth wall; don't assume it must be painted white.
Paint cheerful stripes or contrasting colored panels on the wainscoting. Again, use colors that echo other colors in the bedroom to achieve an uncluttered look. Choose from the dozens of faux finish effects available if you're feeling creative, for a more dramatic, unique look.