mik2718 is correct. There is no internal illumination of the auto labels on any V. However, there is a small LED in the upper console that should be on and provides some illumination of the auto. Caddyscat has the best advice - that is, look at the gear indication in the gauge cluster.
It should also be noted that the small dots in the door opener buttons do not illuminate at any time. They do on the DTS when the dash lights are on, but not on the 2009 and later CTS-V. In fact, unlike the DTS, there is no wire going to the connector that connects to the door opener module on the V. The connector has three positions but only two are used on the V (all three are used on the DTS and one wire carries the dash light voltage when the dash lights are on).