Anybody with an Android device (usually it doesn’t matter which OS and/or ROM you are running) has encountered the situation, when status bar icons (e.g. WIFI and/or GSM/UMTS) are either blue or gray/white. On a sidenote: whether it’s gray or white depends on the OS and the color settings, so from here on I will just write using the word “gray”.
Throughout the internet you can find various answers to the question why icons are either blue or gray. The short explanation is this:

• BLUE: the device is “connected” to Google services
• GRAY: the device is NOT connected to Google services

So what’s the long answer then, and what does it mean to be connected to Google services?

Android devices commonly run several apps or services that require authentication with Google servers in order to sync data, for example Gmail, calendar entries, contacts and certain settings. All those different apps usually use your Google account that is entered during one of the first times you use the phone. And if the authentication with Google servers doesn’t work (for whatever reason), those applications won’t be able to sync. Because this is sort of a major issue (and Google would like you to use as many shipped Google apps as possible on the one hand and wants you to know that it can’t sync on the other hand) Google will let the user know whether it’s able to sync by turning the bars blue if yes, and gray if no.

There are many different reasons why the device is unable to communicate with Google [authentication] servers (and thus the icons turn gray).

• no data connection (so no WIFI and no GPRS/EDGE/UTMS)
• no roaming (and therefore no data connection)
• you are on a WIFI that requires authentication (which you haven’t done, yet)
• the WIFI you’re on only permits HTTP traffic
• you messed up internal settings in an attempt to restore system settings from a different ROM
• many more …

If bars are gray, some data connection will still work whereas other services (e.g. certain push notifications source) won’t.
So if you’re having trouble with blue bars (and Google authentication), check the above list for possible reasons.