  To improve the perception of hierarchical structures in data sets, several
color map generation algorithms have been proposed to take this structure into
account. But the design of hierarchical color maps elicits different
requirements to those of color maps for tabular data. Within this paper, we
make an initial effort to put design rules from the color map literature into
the context of hierarchical color maps. We investigate the impact of several
design decisions and provide recommendations for various analysis scenarios.
Thus, we lay the foundation for objective quality criteria to evaluate
hierarchical color maps.
