I'm trying to use this technique to keep variables separated between different notebooks. It seems to be working fine, except that variables turn black as soon as they are evaluated — any ideas why this would be happening? Here are some examples:

And with a variable that hasn't been used at all:

Suddenly it's black, even though it has no value:

Options[$FrontEnd, AutoStyleOptions](also see in the options inspector) – rm -rf♦ Oct 26 '12 at 20:13