The book by Bente Lange on The Colours of Copenhagen has a section on the pigments used to make grey paint. On historic buildings in the city, the range of greys used is amazing from soft stone colours through dark steel grey to warm greys tending almost to dull green. Of course the pigments used are never simply black added to a white base but might have touches of Prussian blue or ultramarine or even Italian red.
Bente Lange describes the ‘grey of the Baroque’ as ‘a cold heavy colour made by mixing carbon black into white’ and she refers to a painters’ handbook from 1799 that ‘contains recipes for mixing … silver grey, linen grey and ordinary grey’ and there are evocative gems just dropped in to the short account of grey pigments that ground black was made ‘by charring young shoots from grapevines’, linen grey was with white lead, varnish and Berlin blue ‘ground separately before mixing’ and stone colours might include ‘shavings’ from cut stone in lime putty with ‘brown ochre as needed.’
Bente Lange, The Colours of Copenhagen, published by The Royal Academy of Fine Arts School of Architecture Publishers in 1997