Being able to view wind direction is very useful. For example, if you can see a fire near-by to your watch zone, you may want to see the wind direction to check whether the fire is likely to reach your watch zone.
To view the wind direction,
1) From the home screen, select your watch zone
2) Select "Filter" in the top right-hand corner on the app and the top left-hand corner on the website
3) Select "Wind Direction"
4) Select the "X" to take you back to the map view
You can then zoom on the map, or select the Incidents list on the bottom to see the arrows next to icons.
The reason the background may be coloured is because it gives direction and the speed in km/h and knots.