Refs #370: decrease the colour palette on Zepu skin.

The original colour palette had at least 27 colours. Now it has around 16 colours, most of them being shades of gray: 
#000000
#333333
#444444
#555555
#761818
#777777
#999999
#BFBFBF
#CC0000
#DAC003
#FFFFFF
BLUE
GREEN
ORANGE
#EEE
#DDD.