  Color is one of the main visual channels used for highlighting elements of
interest in visualization. However, in multi-class scatterplots, color
highlighting often comes at the expense of degraded color discriminability. In
this paper, we argue for context-preserving highlighting during the interactive
exploration of multi-class scatterplots to achieve desired pop-out effects,
while maintaining good perceptual separability among all classes and consistent
color mapping schemes under varying points of interest. We do this by first
generating two contrastive color mapping schemes with large and small contrasts
to the background. Both schemes maintain good perceptual separability among all
classes and ensure that when colors from the two palettes are assigned to the
same class, they have a high color consistency in color names. We then
interactively combine these two schemes to create a dynamic color mapping for
highlighting different points of interest. We demonstrate the effectiveness
through crowd-sourced experiments and case studies.
