Dithered

Keeping in mind the minimum target configuration of 256 colours the pictures mode was changed from thousands to 256 colours. This sort of a conversion gives a very dithered look to the picture.

Being able to apply lossy compression to parts of an image affords a whole new realm of control: only areas in an image that have a very dithered texture, such as beaches and streets, can benefit from lossy compression, as can dark areas where the human eye is less capable of distinguishing hues.

If users have their monitors set to 16-bit and they're looking at a 24-bit color, they get a dithered color also, but the higher resolution of 16-bit versus 8-bit means that the computer can choose closer colors, so the dither doesn't look as obvious.