About badge background colours:
* black - price did not change from last fetch.
* green - price went up
* red - price went down
So... green is good, red is bad ;)
Depending on the rate it might not fit very well. Just right click the icon, select "Options" and from there select your desired price precision.
Also added possibility to configure notifications so user gets notified when price rises over or falls below configured threshold. Once the limit is met, user is notified and the limit is set to that value - and this is repeated every time new limit is crossed. Go disable the notifications or set a new limit if you get annoyed.