On Wed, Nov 21, 2018 at 3:02 PM Jan U. Hasecke <juh+ntg-context@mailbox.org>
wrote:

> Am 19.11.18 um 11:14 schrieb luigi scarso:
>
> > Perhaps this is still useful
> >  https://www.tug.org/TUGboat/tb31-3/tb99scarso.pdf
>
> Thanks a lot for the hint.
>
> I don't understand the equations but at least I found transicc to
> calculate color conversions.
>
> What precision is useful in the wild?
>
> I now use three digits after the decimal point, eg.:
>
> \definecolor [hs-logoblau] [c=0.976, m=0.665, y=0.028, k=0.116]
>
> It's safe to specify a color as 8bit per channel rgb, or in percent. i.e.
see for example
https://en.wikipedia.org/wiki/List_of_colors:_A%E2%80%93F
(more on  https://en.wikipedia.org/wiki/Lists_of_colors )

16bit per channel rgb are also possible, but old RIP can have problems
 (for example
https://www.pantone.com/color-finder/#/pick?pantoneBook=pantoneSolidCoatedV3M2
shows rgb 8bit per channel  and CMYK 0 to 100)

Btw: be careful of the  checker shadow illusion
 https://en.wikipedia.org/wiki/Optical_illusion
colors not always look as they are expressed  in numeric form.

-- 
luigi