In the world of NTSC video via composite, S-video or component video connections you essentially have two images that are being processed, color C and luminance Y. Luminance is the b/w portion of the image. It takes more time to process the color than the luminance so a timing delay is required to get the color to lay perfectly on top of the luminance. If this is not setup properly then you will get intermittent edging artifacts. Most displays do not allow this to be adjusted and some DVD players provide it but only as a whole rather than separate red, green and blue adjustments. New generation scaling can provide this level of adjustment and varies with manufacturer and model.
The Avia Guide to Home Theater calibration DVD provides a specific pattern for testing, documentation of error and adjustment.
Y/C delay does not exist in the RGB domain such as a computer monitor or CRT front projector nor in the computer generated RGB sources feeding them. If you are experiencing this artifact then it is from a commercial entertainment video source and/or the processing in your system.