Wall color, or paint color, is influenced by so many things that it is imperative to try before you buy. The size of the room, the height of the ceilings, the type of light bulbs you use, the flooring, the furnishings, the reflective qualities of the paint itself - to name a few, can all affect the way light plays against a wall color.
That's why a color that looks great in one home can look totally different in another.
And then there are our human eyes... they are different too. Some people can see the full color spectrum and some people are limited. So you can see how complicated it can get.
After you have figured out all of the above, there is still a huge color changing factor - probably the biggest - and that is the natural light you receive. The direction your room faces and even the geographical area you live has a big effect on your wall color.
A room that has a northern exposure has light that is harsher, more indirect and cooler. Colors can appear gray (especially in northern climes). They can be challenging to decorate, but trying to counteract the cool, gray effect may be the best bet. Northern light is a little bluish. It tends to wash colors out.
You can try to counteract this with colors that have their own warmth. Yellows, pinks, corals, warm russet tones may be able to brighten a north facing room.
Alternatively, don't fight the natural light. Go for a cozy or dramatic look with deep dramatic colors.
Try deep grays, navy, charcoal, hunter - and enjoy the gift of nature.
Remember to try before you buy. A small swatch of color with a nice white border will give you an idea of how the light will play with your color.