in three pixel per byte mode, the sprite may contain 16 colours with the limitation that each set of three pixels must use colours from the same row.
Images can use one of four pixel formats with 2,3,4 or 8 pixels per byte

All images use a MicroPalette of 2,4 or 16 colours. Each entry in the MicroPalette can refer to any one of the Arne16 palette. Middle click on the palette control to reasign the entry

If the MicroPalette Entry #0 is set to the Arne16 #0 (Black) color #0 is transparent. Any other MicroPalette entry set to #0 will be black

The 2,4 and 8 pixel-per-byte formats can have any pixel set to one of 16, 4 and 2 colours respectively. The 3 pixel-per-byte format may use all 16 colours but each byte(3 pixels) must use the same set of 4 MicroPalette colours of

You may map multiple MicroPalette colours to the same Arne16 palette entry.