If the curved "wifi" bars at the top of your Live View changes color, it's measuring the quality of your device's connection to your wifi network. The three colors the bar can turn are:
Green: This indicates that you have a strong connection to the network and should experience no problems using the Live View function.
Yellow: Your network connection is weaker than it should be. You may experience some problems with your Live View.
Red: Your network connection is extremely weak or sporadic. You may experience severe problems including a black screen with your Live View.
An example of such a message can be seen in the image below:
Note that it is possible to see these bars on both the device and your mobile device. Having the bars on the device indicates a weak connection between your device and your router. You may want to check your device's cable or wifii connection. If the bars are on the mobile device symbol, it indicates your mobile device has a weak connection to the internet. Try moving to a location with a better connection or connect to wifi.