I prefer VMC Basalt Grey as the base colour for my 15mm grey tanks and things.
(https://1.bp.blogspot.com/-L95L6HSySBg/WTtwfptf5jI/AAAAAAAAIQc/1txpfvmy09cC015yUNjTK787a8J3iD9OwCLcB/s1600/20170610_marder3ausf139-001.jpg)
I've seen original colour photographs (i.e. not colorized) from WWII, from Signal mostly, showing German tanks in greys from a relatively pale blue-grey right up to a dark, almost black grey. You've got a fair amount of leeway; my preference for Basalt Grey is just that — a personal preference.
Here's a photo from either just pre-war, or very early in the war, of a bunch of grey-painted stuff on parade.
(https://1.bp.blogspot.com/-EQXhvlsuauA/XhfFUBdme_I/AAAAAAAAN2c/BIJpEvzj1asR-np62VIumQX1fW39ONuwwCLcBGAsYHQ/s1600/2020-01-10_GermanParade.jpg)
The rounded noses of the Panzer II on the transports mean that they're very early models, and I'm not sure any of those first version were ever actually in action. There's a slight green cast to the whole photo, not uncommon to old slide film, but the tone of the grey is more important in this case than the precise hue.
A photo like this is useful because there's a complete range of tones present, from the blacks of the tankers' uniforms up to the pure white on the cenotaph, so we can be reasonably sure that the grey tones are fairly accurate.
Here's a photo from either just pre-war, or very early in the war, of a bunch of grey-painted stuff on parade.
(https://1.bp.blogspot.com/-EQXhvlsuauA/XhfFUBdme_I/AAAAAAAAN2c/BIJpEvzj1asR-np62VIumQX1fW39ONuwwCLcBGAsYHQ/s1600/2020-01-10_GermanParade.jpg)
The rounded noses of the Panzer II on the transports mean that they're very early models, and I'm not sure any of those first version were ever actually in action. There's a slight green cast to the whole photo, not uncommon to old slide film, but the tone of the grey is more important in this case than the precise hue.
A photo like this is useful because there's a complete range of tones present, from the blacks of the tankers' uniforms up to the pure white on the cenotaph, so we can be reasonably sure that the grey tones are fairly accurate.
It actually shows the 2/3 dunklegrau (RAL 7021) , 1/3 dunklebraun (RAL 7017) scheme used from 1938 to mid 1940. It's particularly evident on the tank transporters but other photos from the same (or similar) parades show widespread use. http://www.missing-lynx.com/panzer_facts.htm The parade date is stated to be 20th April 1939.
(https://blog.done.gr/wp-content/uploads/2015/05/Hugo-JAEGER-Photographe-personnel-Hitler-42.jpg)
From https://blog.done.gr/history/hugo-jaeger,with details of the photographer.
Fitz, the early models were used in Poland where their thin armour proved a problem. The survivors were often rebuilt with better armour.
(https://www.worldwarphotos.info/wp-content/gallery/germany/tanks/panzer-2/destroyed_Panzer_II_Poland_1939_2.jpg) 2 ko'd PzII from Poland.
(https://www.worldwarphotos.info/wp-content/gallery/germany/tanks/panzer-2/Panzer_II_ausf_b_poland_1939.jpg)
and an even earlier preproduction model (ausf b), again from the Polish campaign.
(https://upload.wikimedia.org/wikipedia/commons/8/8d/Bundesarchiv_Bild_101I-382-0248-33A%2C_Im_Westen%2C_Panzer_II_und_Panzer_I.jpg)
This is a rebuilt one, with angular nose armour, no cupola, which was sometimes also added. France 1940.
Apologies to the mods for the 'crooked crosses', a bit hard to avoid in the context!