Since most computer monitors and television displays have different color ranges, the same image on a computer display can appear very different on an NTSC or PAL monitor.
Colors appear much brighter on a television display. This is because video uses a different gamma curve for luminance than a computer monitor. Also, most computer monitors use RGB color space, and television displays use YUV color space.
Some pure colors, such as red and yellow, can cause bloomed (very saturated, fuzzy) images. In some cases, colors can cause interference with broadcasting, which is referred to as NTSC illegal colors.
