In this photo from a December 11, 2008 Marxist.com article, the protesters can be seen giving the communist fist salute. Marxist.com is obviously a pro-communist website.
And here they are with large red flags...
"After four days of struggle we can now start to draw some first clear conclusions. Without any doubt this movement deserves the title of 'teenager uprising'. We have here a new generation of tens of thousands of school students erupting in a huge explosion, the biggest for 20 years, if not even more, in Greece. We have clear symptoms of an instinctive revolutionary spirit, and a clear tendency to target not only the present bourgeois government but also the bourgeois state and the capitalist system as a whole."
http://www.marxist.com/greece-teenager-uprising-big-general-strike.htm