[Qgis-user] Variables for colour values

[Mofo Yoda]

I wonder if it’s possible to use variables for colour values, line widths etc? I have rule-based styling with lots of rules, and I want to change the colour value in one place and not in every rule that uses the same symbol. I’ve been using variables a lot in CartoCSS styling, but I really miss them in QGIS. Since I can define project colours with names in QGIS, i thought it may be possible somehow.
I’m on QGIS 2.8 for OS X.