Slitherine

I understand the red circles mean your units are cut off from supply but, what do the yellow ones mean?

IIRC, the green/yellow/red circles reflect fatigue and fighting efficiency.
Green - Full supply/No fatigue full fighting efficiency.
Yellow - Fatigued / Reduced Supply - Reduced Fighting efficiency.
Red - Severly Fatigued / Low or no Supply. VERY Reduced fighting efficiency.

Units go from Green to Yellow due to under supply (more deployed units than supply capacity), continued attack/defend or extended movement over rough terrain. You need to let units rest without movement/combat or reinforcement for a turn to get them back to Green.

Units go Red when out of Supply, suffer heavy losses or heavy bombardment.

There are two interacting systems. The circles only refer to supply. The colour of the strength number refers to efficiency. Reduced/no supply status quickly lowers efficiency over turns.

Cool, thanks for the clarification.