I don't know where that idea comes from, but I doubt it.
Since flipping the color/B&W switch has an effect, the switch itself is ruled out as being the cause. Most likely the console is NTSC. Can you post a picture or the full text of the label on the bottom? If it's missing, the next best thing would be a photo of the motherboard.
Hi there - the text on the bottom says:
MANUFACTURED FOR ATARI INC.
BY DIMERCO ELECTRONICS IN TAIWAN
MODEL CX-2600 P
COVERED BY US PATENTS 3793483, 3900886, 3723652, 372480, RE 28507, RE 28598 & PATENT PENDING
SN 407369