The arrow color and species color can be set as a preference. Changing these colors alters the coloring scheme of the Reaction Path Diagram. The second color option will color a reaction connection logarithmically according to heat rate of production, with positive heat being red, and negative heat being blue. The remaining color choices indicate which of these side species are involved in a reaction line that connects two species in the diagram. An example of a diagram colored by side species is shown in Figure 4.12: Path diagram. With connections colored according to the presence of a side species in a reaction.