Color manipulation

[CKY-2K/Clay Man]

Some games, or some effects minipulate the color spectrum into different tinting. How is this and why?

You're supposed to be limited to about 56 colors but in some situations you can manipulate the palette into a tint, like this one "blue tint" Game Genie code for Super Mario Bros.

[strangenesfreak]

The color emphasis bits in PPU register $2001 can sort of "emphasize" red, green, and blue, or combinations of those (red+green= yellow, red+blue= magenta, green+blue= cyan, all bits set= just darkens the palette). You can see those bits at the $2001 section in the NES PPU wiki article.

I've read that the PPU actually darkens the colors when those bits are set, so "emphasizing red" is really deemphasizing cyan, "emphasizing green" is really deemphasizing magenta, "emphasizing blue" is really deemphasizing yellow, etc. More information on that is at the NTSC Video article's Color Tint Bits section and at the PPU Voltages thread here.

[Zepper]

Probably because a lot of sites bring wrong information about the NES. Usually, they copy/paste the things without any strict argumentation.

[jwdonal]

FYI: The color tint bits section on the wiki has been moved here.