how's this?
Test image: note +/- I bars and +/- Q bars in upper left (Y, I, Q all full bandwidth)
Q turned off (transmitter side, I filtered at to 1.5 Mhz bandwidth):
I turned off (transmitter side, Q filtered to 0.5 Mhz bandwidth):
Encoded and decoded with I/Q demods, subcarrier notch filter in Y channel, shows: cross color in awning; Q smear on green-magenta edge; subcarrier dots on color bar edges.
NOTE: computer simulation was simplified by making the color subcarrier phase coherent with the pixel placement in these images, resulting in the slight aspect ratio distortion seen here.