As we don't have 4k HDR images from actual, in-the-field 1941 Panzerkampfwagen, we kind of have to guess. Yes, the colour is grey, but which grey? Is the sun shining, or is it getting dark? That will influence how the colour is seen! And don't mention non-colour-calibrated monitors, all set up slightly different. What is vibrant Kermit green on one, is drab khaki on another screen. That does not help me either! And I'm quite sure there is no totally fresh, unaffected 1940ies RAL7021 paint chip available... (Oh wait, we DO have one for 1944 DG-III! It's at Bovington, they have a periscope in that colour, that was boxed for seventy years. Opening the box forced them to re-paint that late war Panzer in the correct shade of yellow.)
In my case, I guesstimated base colours from a mix of actual RAL values, Tamiya AS paint, a book and Panzerbaer's excellent overview & then used a web colour kit to derive lighter and darker variations. So these are the colours I defined, and I'll use them consistently in my factory fresh models.
RAL 7021
Dunkelgrau
RAL 8020
Sandbraun
RAL 7028
Dunkelgelb '43
RAL 7028
Dunkelgelb I '44
RAL 7028
Dunkelgelb III '44
RAL 8012
Rotbraun
RAL 6003
Olivgrün
RAL 6011
Resendagrün A
RAL 6011
Resendagrün B
RAL 7008
Khakigrau
RAL 8000
Grünbraun
RAL 8002
Signalbraun
RAL 8017
Schokobraun
Steel
Glass
Rust
Mud