The significant difference here is that images seem to be rendered differently to paragraph background colours. With images readers seem to dither their 8 or 16 greys, which is what you would expect from image rendering with a limited palette.
However, with background-color style there seem to be different approaches. My PRS-300 dithers, hence the 'smooth'/'grainy' results, whereas other readers seem to snap to the nearest grey that is not dithered. Both methods are valid but produce different results.
I'll test more with my PRS-300 and KPW to try and find a good compromise - at least I can ensure that my grey background paragraphs don't end up white!
Thanks for all the info.
("seem" = 'educated guessing')
Last edited by Agama; 01-17-2013 at 04:07 AM.