Best color to paint wall in rental property?

If, and only if, your rental agreement allows you the freedom to paint your house then you may paint it whatever color you find appealing.

Most rental agreement allow you to paint (the interior) any light or neutral color within reason.

If you choose to paint a darker color or one that is unusual, be prepared to return it to the ordinal color (repaint before you move out).

Most people do not stay in a rental unit for extended periods of time and therefore choose not to paint twice, once when they move in and again when they move out (to return the unit to its original color).

As for the exterior of your rental house, I suggest you talk to your landlord. Exterior painting is not usually undertaken as often as interior painting, there are frequently restrictions on the color/colors that can be used, and in many cases the landlord will either pay for the paint (you supply the labor) or hire the job done.