Haven't found any evidence about commercial colors other than they
need to meet NTSC standards:
http://en.wikipedia.org/wiki/Television
http://www.ntsc-tv.com/ntsc-main-01.htm
http://en.wikipedia.org/wiki/NTSC
For backward compatibility with black and white television, NTSC uses
a luminance-chrominance encoding system invented in 1938 by Georges
Valensi. Luminance (derived mathematically from the composite colour
signal) takes the place of the original monochrome signal. Chrominance
carries color information. This allows black and white receivers to
display NTSC signals simply by ignoring the chrominance. In NTSC,
chrominance is encoded using two 3.579545 MHz signals that are 90
degrees out of phase, known as I (intermodulation) and Q (quadrature).
The phase relationship of the I and Q signals with the 3.579545 MHz
subcarrier corresponds to the instantaneous color hue captured by a TV
camera; its amplitude corresponds to the color saturation (purity) of
the original signal.
For a TV or a display to recover color information from the varying
phase and amplitude signals just described, a constant phase reference
3.579545 MHz signal is needed. A short sample of this reference signal
is included in the NTSC signal as colour burst, located on the back
porch of each horizontal line, the time between the end of the
horizontal synchronization pulse and of the blanking pulse on each
line. The colour burst consists of a minimum of eight cycles of the
unmodulated (fixed phase and amplitude) color subcarrier. By comparing
the reference signal derived from colour burst to the colour signal's
amplitude and phase, colour hue and saturation information are
recovered.
When NTSC is broadcast, a radio frequency carrier is amplitude
modulated by the NTSC signal just described, while an audio signal is
transmitted by frequency modulating a carrier 4.5 MHz higher. If the
signal is affected by non-linear distortion, the 3.58 MHz colour
carrier may beat with the sound carrier to produce a dot pattern on
the screen. The original 60 Hz field rate was adjusted down by the
factor of 1000/1001, to 59.94059... fields per second, so that the
resulting pattern would be less noticeable.
Another important factor in choosing a new field rate (59.94 Hz) was
to reduce interference between the chrominance signal and the audio
carrier. The chrominance signal is an n + 0.5 multiple (exact 227.5)
of the line frequency to minimize interferences between the luminance
carrier and the chrominance carrier. The audio carrier is an integral
multiple (286.0) of the line frequency to minimize interferences with
the chrominance signal, which is a n+0.5 multiple of the line
frequency. Because the audio frequency was defined by the former black
white standard (4.5 MHz) and the exact audio carrier was much more
critical than the exact field rate, the field rate was moved from
60.00 Hz to 4,500,000 Hz / 286 / 262.5 = 15750 Hz / 1.001 / 262.5 =
15734.26573... / 262.5 = Hz = 59.94005... Hz = 60 Hz / 1.001 Hz.
Now...for commercials there are colors that advertisers try to avoid
(but there is no 'law' about it)..ie red in feminine napkin
commercials, white cars etc....it that more your question? |
