the color problem is a bug in the current gem version (I have the same problem). You can try to take the old gemversion you were using before and replace the buggy one.
Is there a simple way to take Gem from the pd-extended instalation that where it works, and stick it in the Pd-extended instalation where it doesn't? I was looking through the directory where pd is intalled and couldn't find an obvious place (I'm very new to mac so I'm still struggling with where everything is and how to make changes. I looked for compiled versions of Gem and there aren't many for mac, and I can't even see which version of Gem is the one that's working because loading the old pd creates problems with new pd).
the problem with demux is, that it is an abbreviation for demultiplex, and
I don' think I am using demux in that patch.
Oded