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variable: $ipsiyellowfact -- ipsi yellowing
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default: 0.0

The "iy:" entry (middle right) changes the
ipsilateral fade out from gray to various amounts
of yellow.

Setting $ipsiyellowfact to 0.0 gives pure gray
while setting it to 1.0 gives pure yellow.

The range of phase angles or both gray and yellow
is controlled with $fadef ("fad:" entry).
