Now, another reason to make color boxes like these is to get a feel for not just
whether the colors clash but also to figure out if they play any eye‑tricks on you when
they are put on top of one another. Some colors, when they are superimposed, will
have certain visual effects that aren’t desired on your map. When it comes to GIS
maps, these effects are not as noticeable as they are to those in other graphic design
fields, but it is still important to have a cursory understanding of what they are and
what causes them.