Lechuza is my favorite brand of self-watering planters. I have one Lechuza Classico Color and a Lechuza Cubico Color Garden Planter. Both are white.
In addition to blending in anywhere, they are of high quality and made to last. They can stand sun, heat and freezing cold without changing color or breaking. This makes them ideal for use indoors as well as outdoor. The water level meter is easy to read even from a distance. They hold large volumes of water and usually only need refilling once a month or so.
Yeah I think white is good. Even the earth tone colors would be good depending on how well it matches with your home or if outside then the soil and the natural flora around it.