-------------------------------------------
switch variable: $colscale -- funct color scale
-------------------------------------------
switch value: 8 => RYGB wheel (complex data)

The "w2" (wheel2) color scale designed for
phase-encoded data (e.g., retinotopic mapping
data).  The scale is:

  Red -> Yellow -> Green -> Blue -> Red

Setting angle_cycles > 1.0 results in multiple
cycles through the scale.  Fractional numbers do
not wrap gracefully.

