Once the print colour has been changed there is no way to bring it back ‘by layer’.
Can you fix it, please?
It is still by layer, no? All you have done is changed the layer print color from default? Are you saying that you can no longer access the color picker to set the layer print color to a different one?
Nope.
I can edit colour any time but I am left without option where, by changing layer colour, it automatically changing print colour (which is set by default).
Still don’t know I am clear enough.
In moment like this my British gf is claiming that I don’t speak English at all… 
Yeah, OK, I see. That must be a Mac Rhino bug, if I change the layer color here on Win Rhino, the layer print color follows the layer color change - IF I have not changed the print color beforehand. If I change the layer print color once, it then becomes independent of the layer display color.
Exactly 