This is why I'm tending to like the Mig Ammo paints more and more, If you can find the shade you want in a modulated series then you can go up and down in darkness without any issues.
The range has 2 rml83's A-MIG-0056 That is the standard colour.
Or it also has A-MIG-0925 it's still RML83 but it modulates with 4 other paints for a 5 paint modulated set.
A-MIG-0924, A-MIG-0925, A-MIG-0926, A-MIG-0927, A-MIG-0928.
https://www.migjimenez.com/en/acrylic-colors/341-olive-drab-modulation-set.html
That 4 colour set is missing the darkest colour in the modulation, A-MIG-0924.
They also sell the full modulated set of 36 paints as a set.
https://www.migjimenez.com/en/acrylic-colors/2312-modulation-colors-collection-17-ml.html
Mig compatibility chart.
https://www.migjimenez.com/img/cms/PDF/acrylic-colors-conversion-chart.pdf