Now, before I go any further, let me warn you that I'm really not all that much of a computer geek, so I can only explain things as I understand them. If you are in true color mode your computer is configured to display up to 16.7 million distinct colors. That gives you a couple million shades of red alone. There is a price to pay however. Your poor computer has to work extra hard trying to display everything.
Consequently things tend to work a little slower and often a little jerkier.
But I gotta admit, images look very good. If you want to give your processor a bit of a break, you can set your computer to display 64,000 colors rather than 16.7 million. This is the high color mode. You get nice looking images, nicely feathered edges and there's not much in the way of jerkiness or slowness in your display. Now if your like me, and super high image quality takes a back seat to speed, and you want your display to take up as little resources as possible, or if you have an older computer, you putz around in 256 color mode.