The SNES and Super Famicom do not have gamma correction hardware, but the N64 does. Some developers have indicated that the colors on the N64 look "washed out" with gamma correction turned on.
If you are currently writing games for SNES or Super Famicom (or any machine that does not have gamma correction), your production path is likely to be setup to compensate for the lack of gamma correction hardware. In other words, you are most likely selecting pre-gamma corrected colors. If you use this same production path and turn the N64 gamma correction on, you will get the washed out effect because you have performed the gamma correction twice.
To undo the first gamma correction, square and shift down by 8 bits, each of the 8 color components (assuming 8 bit color), or rework your path to exclude the gamma correction stop, leaving gamma correction to the hardware.
Every step in your production path must be involved in the color selection process: modeling/paint software, computer monitors, image conversion software, the game software, and the N64 hardware.
Gamma correction on the N64 is recommended; the antialiasing and video hardware work best when it is enabled.