Read these simple steps for calibrating an NTSC monitor in the instruction manual of the Marshall monitor.
1. Allow the monitor to warm up for at least 5-10 minutes.
2. Display SMPTE split-field color bars on the monitor using an external source.
3. Enable Monochrome mode.
4. Locate the pluge pattern (super black, black, and gray bars) at the lower-right corner of the screen. Adjust the Brightness knob until there is no visible difference between the super black and black bars, but the gray bar is still visible.
5. Adjust the Contrast knob until an even grayscale appears along the top bars.
6. Disable Monochrome mode.
7. Enable Blue Check Field mode and adjust the Color knob so that the outermost bars (white and blue) appear to match in brightness.
8. Composite NTSC only: Adjust the Tint knob until the third bar from the left (cyan) and the third bar from the right (magenta) appear to match in brightness.
9. Disable Blue Check Field mode.
Read more info on the Marshall V-LCD70P-HDA 7″ LCD Monitor