You won't see any colour difference in R1 ("NTSC") DVDs or R2 ("PAL") because they both use the YUV colour-space in MPEG2 compression.
But you will see 3:2 pull-down versus 4% speedup; possibley notice lower resolution and resulting overuse of Edge Enhancement; etc. etc.
Corrections: the joke was "never twice same colour" and this refers to analogue broadcast NTSC, as opposed to analogue broadcast PAL, because NTSC used the YIQ colour-space instead of PAL's YUV (and French SECAM uses YDbDr).
YUV colour-space: (Y for luminance, U for blue minus Y, and V for red minus luminance). Note: the YCbCr or YPbPr colour space, used in component video, is derived from YUV (Cb/Pb and Cr/
Pr are simply scaled versions of U and V), and is sometimes inaccurately called YUV because of this. YUV is simply created from an original RGB (red, green and blue) source and is easy to do with analogue equipment: hence it's use since the 1960s.
YIQ colour-space: (Y for luminance, I for in-phase, and Q for quadrature).
YDbDr colour-space: is almost identical to YUV but weighted slightly.
The primary use of these colour-spaces is to remain compatible with black and white televisions sets. However, with YIQ it was also possible to get rid of 89% of blue signal and 60% red and therefore use a much lower broadcast bandwidth -- the result was a need for a "tint" setting on sets to adjust the end-users colour.
Digital pictures don't have the old analogue broadcast colour-space differences, be it broadcast HDTV or DVDs. If you see one on DVDs, it probably down to the ISF calibration of your screen rather than the source material; it's that or your mind is playing tricks on you.
Saying that, I always laugh when I visit the States and turn on the square 4:3 TVs in my hotel rooms -- the scan-lines can be seen from the other side of the room! When I was a kid I always wondered why movies put a special effect of horizontal black lines over television pictures to make screen "look like tv"; until I went to USA and saw that 480 lines doesn't stretch too well over a 28" CRT.
StooMonster