The ral colour you have chosen Nick, is correct for Army. Until end 1942 -Dunkelgrau-dark grey RAL 7021.
From end 1942 - Dunkelgelb - beige - Ral 7028 - no longer available on the present day ral colour system, however, colour matches have been established using samples from original vehicles and equipment.
Individuals tend to guess the shades , hence you get so many variants with vehicle colours within re-enactment.
The other grey you mention may be the airforce grey . 1941-45 Grau - grey RAL 7019.
Africa corps used a RAL 8000 Gelbbraun-dark beige 1941-42
The krad below shows the paint finish in RAL 7021
Colour accuracy only as good as the camera taking the photograph etc.

The samples below are an interpretation [guide only] as computer monitors colour rendition are all different and vary somewhat, depending on how the individual has set the PC.
So if you stick to the paint being mixed to a specific Ral code, the colour should be accurate.
RAL 7021..............................................RAL 7019.................................................RAL 8000.......................................RAL 7028

Hope this information is useful to you.
from the book " Wehrmachtsgespanne gestern und heute "
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