Well, for one thing “it is alive” but the leaves and some of the vegetative structure may be brown or tan.
So, as temperatures fall below 60 degrees Fahrenheit Bermuda will slowly initiate dormancy. Once temperatures drop to between 50 and 55 degrees Fahrenheit, Bermuda grass goes dormant, turns brown and appears dead.
Even though the turf may appear dead the roots and stems remain very much alive and if you look closely you can see the green stems. “They are still working just more slowly”. If it doesn’t rain and conditions get dry you will want to irrigate (water) to prevent desiccation (drying out) of your lawn which will cause turf damage that will be seen in the spring green-up. We call it winter kill.
You can mow or trim your Bermuda turf for aesthetic reasons but please do not scalp your Bermuda. Leave 1 ½” to 2” as a blanket of insulation to protect from possible hard freezes.
If you want your lawn to return to the glorious green color in spring, prepare it to withstand low winter temperatures.