Left: Material with oversaturated colors
Right: Video color check shows black areas that are beyond the video threshold
Such colors tend to blur or fuzz when transferred from computer to video. Pixels containing these "illegal" or "hot" colors are flagged on the sample object.
You can have 3ds Max correct illegal colors automatically when you render, depending on the settings on the Rendering tab of the Preferences dialog.
Use this option as a guide only. The colors in a rendered scene depend not only on the material color but also on the intensity and color of the lighting. A material that shows as safe in the sample slot might become illegal if rendered under several bright lights. A safe practice for video is to use colors whose saturation is less than 80 to 85 percent.