Graphics Reference
In-Depth Information
a secondary node labeled “Pevensie Child,” where all links of this type are
represented the same way and understood to be attributes.
Color
Color is an important dimension of any visualization. The difference
between a visualization with good color choices and one with poor choices is
enormous. Poor color palettes can render a visualization incomprehensible.
Colorchoiceisundoubtedlyanart,butthereisagreatdealofsciencebehind
it that has to do with how we see and perceive.
The principles involved provide a framework for approaching color choices
and, at the very least, should be a basis for recognizing when poor choices
are being made. Principles are by no means prescriptive, however. Within
the guidelines presented here, there is still plenty of room for creative
artistry.
Color Palettes
One primary principle of color choice is that colors come loaded with
import. Colors have both cultural and natural associations that influence
interpretation. If you choose a palette that intuitively fits expectations, the
visualization will be easier to interpret. Palettes that go against the grain of
expectation will cause endless frustration.
Color associations are firstly cultural and, as such, are subject to a certain
amount of variation in cultural expectations. For example, in most business
cultures (not least of which, finance), red signifies loss or bad, and green
signifies gain or good. In military circles, red signifies enemies (also bad),
but green signifies neutral parties, and blue indicates the good guys.
Table 16-1
lists a number of broad color associations to consider when
mapping to data. Notice that one of the themes evident in this list is that
although colors have cultural import, meanings are often rooted in natural
associations.
Two important and related principles of color were alluded to in reference
to red in
Table 16-1
.
Firstly, colors have certain optical properties that make
them more or less noticeable than others, and secondly, this depends a
great deal on the color field surrounding it. Red is the most salient color
on light-colored backgrounds, but the heat map of shipping traffic shown
in
Figure 16-10
shows how this changes on a black background. No legend
