When the color scheme for
this wall behind Mystery Price was first introduced on TPIR, the red stripe was not present. The wall only appeared that way for four days -- one set of tapings.
Sometime early last decade, there was a pink strip across the floor at the base of Contestants' Row for one episode.
When the Hollywood mural was replaced by the pastel Turntable walls, a gigantic yellow circle was stuck behind Clock Game because the chroma key effect used to show the contestant on the board was also keying out part of the wall. It only lasted for two shows before they painted the board and started keying out green instead of blue.
For a few months in 1992, 3 Strikes had white strike chips with red Xs.
For a couple months in Season 28, a cover was placed over the chase lights on Push Over that made them look really weird when they were chasing and like a solid, strangely-angled bulb when they weren't. It showed up on a couple random episodes the next winter, too.
How do producers decide to make set changes, anyway? I can understand wanting to redo your whole set every few years, but some things, like the strip in front of Contestants' Row or making the orange display yellow, just make me wonder, "Why did anybody even bother thinking of that?"