In gvNix there is a printing tool for the map that is the following tag <tool:print id="ps_org_cite_pese_web_Mapa_print"/>
, it works perfectly for me, the question is that when I print the image it comes out in black and white, I would like to know if there is any possibility of obtaining the image in color.
As far as I know, gvNIX does not change any of the color, so it seems to me that it must be the configuration you have set on the printer. Checking can be as simple as printing to a PDF file or trying printing on another computer.
I just tried to print in PDF with chrome the online demo and it worked perfectly for me.
Luck!