Trouble retaining high colour icons

I seem to be having trouble retaining high colour rendition of my icons. My
desktop settings are for 32 bit colour and my desktop wallpaper & program
windows are rendered correctly but my icons are frequently downgraded to 256
colour renditions ( very poor if not 256 colour) which are quite hard to
see.

Does someone understand where this icon colour rendition is controlled from
and how I can stop it from changing to low colour rendition?

Thanks in advance for your attention and help.