Most of the enabled scrensavers in xscreensaver look crappy - not antialiased, rough shapes illustrating mathematical obsessions, using non-matching colours. Get yourself a Mac and compare which screensavers are of decent quality. It would be nice if colours of panel plugins available by default sticked to some colour palette for example Tango known from Guake. At present they use random bright colours chosen rather by their easy to remember and type RGB values and to to match your system.
xscreensaver is not Xfce's consern and we're aware of tango, thank you.