One pixel requires 3 bytes of info for 24bit and 4 bytes for 32 bit i.e., RGB and one byte for alpha channel.

16 bit mode, 2 bytes are used to store the RGB values i.e. 5,5 and 6 bits for each colour. I think green takes 6 bits, someone else can fill that in if it ain't right.


@speeder

When you convert to 8 bit pallete do you force primary colours?

If you do not the fuschia may not infact not be fuschia in which case it won't function as the transparent colour. I used photoshop and when I convert to 256 colour mode I ensure the primary colours are present. I also only "paint" the fuschia into my graphic after I convert to 8 bit colour.