Different version of chromatic number I'm wondering whether or not there is a symbol or value such as the chromatic number of a graph that asks 

What is the minimum coloring of the graph such that not only adjacent vertices have different colors, but vertices adjacent to a mutual vertices have different colors.

I'm just curious on whether this is a thing, or is it question that is easily related to the chromatic number and thus is not really thought much about.

I've seen this called the distance-2 coloring, where distance-k coloring asks for a vertex coloring where every two vertices of the same color are more than k steps apart. It's used in algorithms and computational results, but I'm not familiar with many of its properties.
