Red stars that get redder

[Michael Sallman <msallman@pro-ns.net>]

I've run across a couple of M variable stars in the database that look to
have significantly larger Ic amplitudes than V. I thought that normally their
amplitudes were greater in V. What would cause this phenomenon?

The stars are GY Del:
http://sallman.tass-survey.org/servlet/markiv/template/TassPlot.vm?object_id=2870811
and V0646 Cyg:
http://sallman.tass-survey.org/servlet/markiv/template/TassPlot.vm?object_id=3773712

Lokking at the ROTSE/NSVS data for V0646 Cyg, it also has a smaller amplitude
than TASS Ic, though it's only 1 cycle:
http://skydot.lanl.gov/nsvs/star.php?num=5925853&mask=32004

I also checked Simbad and Google, but didn't find anything on these stars.

Thanks,
Mike