Note that if you don't have enough memory for more than 256 colors your computer can slow to a crawl since it will be accessing the hard drive as virtual memory every time you load a new screen.

When my mother got her first Windows computer it had only 32MB and 256 colors. It displayed a lot of things OK and some badly. I set it to 16 bit color and it slowed down. I called around the city and found a dealer who had that kind of memory at a reasonable price. It was the dealer who put the computer together! With 80MB in it it was OK. But on some sites parts of images still looked bad because they were intended as 32 bit images and with 16 bit it chose 256 best colors for each pane and some gently shaded parts had artifacts like layers of shelves.

When I worked at a charity as a secretary I found their Win98 computer made of surplus parts was so slow, it could not access the internet as a practical matter. It had 16 bit color and not enough memory. I reduced it to 256 colors which made the default cloudy sky desktop an ugly mess. I went home and composed a wallpaper of the charity's corporate logo in the 16 default colors and put that up. I tweaked the old machine till I had tripled its speed.