If it's greyed out, you are not connected. If it's normal color (black) then you are connected. Also, next to your carrier name, it will display "- WiFi Network Name ". I hope this answers your question.
Not so. Do you have the name of the wifi network on the screen? If so, the device is connected to the wifi, even if greyed out. The bolded wifi means you have a connection to the wifi and a Blackberry data connection through the wifi as well. Bold wifi vs. greyed wifi is the same as the difference between EDGE and edge.
The logo doesn't change color when just connected to your router/internet. It's connected when it shows the name of the wifi network. Bold means a data connection is established over the wifi. UMA means you have voip.