Most modern day Cathode Ray Tube (CRT) televisions manufactured after the 1960s (after the introduction of NTSC and PAL standards) supported the circuit-based decoding of colored signals. It is well known that the new color standards was created to permit the new TV sets to be backwards compatible with old black and white broadcasts of the day (among also being religiously backwards compatible with numerous other legacy features). The new color standards added the color information on a higher carrier frequency (but at the same duration of the luminosity). The color information is synchronized after the beginning of each horizontal line and is known as the colorburst.
It would seem that when you feed noise into a television, the TV should create not only black and white noise but also color noise as there would be color information at each new horizontal line where each frame should be. But this is the not the case as all color TVs still make black and white noise!
Why is this the case?
Here is an example signal of a single horizontal scan.
And here is the resulting picture if all horizontal scans are the same (you get bars!).