The concept of double chromatic refers to a property of graphs, which are mathematical structures consisting of vertices (points) and edges (lines) connecting pairs of vertices. A graph is said to be double chromatic if it can be colored with two colors in such a way that no two adjacent vertices have the same color and no two vertices at a distance of two have the same color.
In other words, a graph is double chromatic if its vertices can be colored using only two colors (usually, red and blue), in a way that no two adjacent vertices have the same color and no two vertices that are exactly two edges apart have the same color. The double chromatic number of a graph is the minimum number of colors required to achieve such a coloring.
The concept of double chromaticity is used in various areas of computer science, including graph theory, computational geometry, and image processing, as well as in some applications of coloring problems, such as scheduling and timetabling.