Apple Color 1.5 - Manual (Page 191)

The Parade scope is also useful for comparing the relative levels of reds, greens, and blues
between two shots. If one shot has more red than another, the difference shows up as
an elevated red waveform in the one and a depressed red waveform in the other, relative
to the other channels. In the first shot, the overall image contains quite a bit of red. By
comparison, the second shot has substantially less red and far higher levels of green,
which can be seen immediately in the Parade scope. If you needed to match the color
of these shots together, you could use these measurements as the basis for your correction.
An elevated red channel betrays the degree of the color cast.
An elevated green channel reveals a different correction to be made.
The Parade scope also lets you spot color channels that are exceeding the chroma limit
for broadcast legality, if the Broadcast Safe settings are turned off. This can be seen in
waveforms of individual channels that either rise too high or dip too low.
191 Chapter 8 Analyzing Signals Using the Video Scopes