Why do some cobs and breeds have 555 and 565 sprites available?
This means that creatures can be played on a wider range of video cards, older ones that support the 555 encoding and newer ones that use 565. If you’re not sure which you use, download both sets and then use one. If the object or norn looks green and strange in your world, you need to use the other lot. If they look fine, then you’ve got the right sprites and you know which ones to download next time.