-------------------------------------------
variables: set explicit colors for "bi" colscale
  --------- r,g,b for OFF phases
  $colr1
  $colg1
  $colb1
  --------- r.g,b for ON phases
  $colr2
  $colg2
  $colb2
-------------------------------------------

The "bi" colscale by default uses green for OFF
phases and red for ON phases.

Arbitrary colors for OFF and ON in the "bi"
colscale can be specified by setting these 6
variables before redraw.
