Took 2 seconds to google search, just a tip for the future
From what I understand, That application only works on the ORIGINAL 8100, not any of the "Pearl 2" series (8120, 8130, etc). They don't have the colored LED's under the Trackball on the newer series to allow you to change the color.
To OP, you might want to look at cnn.cn I've seen other posters referred there for replacement trackballs. Click the link below, they have several different trackball REPLACEMENT colors to chose from.