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switch variable: $colscale -- funct color scale
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switch value: 18 => ORBGY wheel (complex data)

The "w4" (wheel4) color scale was designed by
Fred Dick for auditory cortical maps (complex
data).  It has more colors than the standard
green-blue-red wheel, and a built-in gray region
at the phase wrap-around point.

The scale is:

 Gray -> Orange -> Red -> Blue -> Green -> Yellow -> Gray

The scale can be rotated with $angle_offset,
reversed with $revphaseflag, and 180-deg flipped
with $invphaseflag.  There is no effect of
$angle_cycles, $fadef, or $ipsiyellowfact.
