In most cases, the device has an internal sync generator which must be genlocked to your system. There are many types of devices with many types of needs. These rules apply to PAL and NTSC and are slightly modified for any component type of system. Encoded color systems like NTSC and PAL require sync and subcarrier at a minimum for locking a color signal. There are some tricky ways to combine the requirements into one signal.
Black burst is the most common combination signal.
Color Bars or almost any other stable color video signal will probably work in place of black burst for generator locking purposes. Encoded video systems usually require Black Burst, locked to the master generator, for reference or genlock. If the system is black and white, then sync is usually all that is required. One major problem is we don't have a standard for labels. At Videotek, we have our own internal standard for labels on any product, so at least we're consistent.