When multiple sample classes need to be visualized on a heatmap, it is useful to be able to distinguish them by color. This function generates a set of colors for sample classes
Arguments
- n_group
 how many groups should there be colors for
- randomize
 should colors be randomized? (default is
NULL). See details.
Details
the default for randomize is NULL, so that reordering
  the colors randomly is decided purely based on the number of colors requested.
  Currently, that cutoff is 5 colors, less than that the colors will
  always be in the same order, for 5 colors or more, they will
  be in a scrambled order, different each time unless set.seed is
  used. If randomize is TRUE or FALSE, then it overrides
  the defaults.