Slitherine

Sometimes the strength number on the unit icon is colored white, sometimes yellow. What does this mean?

Sometimes the unit icons have a circle in the bottom right corner that is half shaded and half clear. What does that mean?

Finally, not a unit question, but a gameplay question. When you land troops via transport for an amphibious invasion how do you keep them supplied? I'm trying to take over Norway as the Axis and it's tough.

The strength color indicates the efficiency of the unit.
60+ = white
40-59 = yellow
20-39 = orange
0-19 = red

The higher efficiency the more damage the unit does in combat. Shock damage from BB's, tac bombers and armor will reduce efficiency of the unit. You also lose efficiency while moving, fighting, being transported by rail or sea, upgrading etc.

The circle in the right corner shows the supply level.

No circle = supply level 4 or 5
Half white/half black circle = supply level 2 or 3
Black circle = supply level 1
Red circle = supply level 0

The supply level affects many factors including the movement allowance, number of steps you can repair and efficiency regain.

You get supply level 5 if you can trace a contiguous land line of max 20 hexes to the primary capital of your side. Berlin or Rome for the Axis, London, Washington or Paris for the Allies and Moscow for the Russians. Notice that the primary capital moves to the secondary capital if captured.

You get supply level 4 if you're between 21-40 hexes from the primary capital. You get supply level 3 if you're more than 40 hexes from the primary capital.

If you can trace to a city you get supply level 3. Port cities will give supply level 3 overseas. If you place a CV, BB or DD adjacent to an overseas land hex then you give supply level 1 to that hex and all other controlled hexes linked to this hex.

So when you try to take Norway you should move a BB adjacent to the invasion hexes near Oslo and have supply level 1. When you capture Oslo the supply level will increase to 3. Since Norway will surrender you get control of all Norwegian hexes and they will also get supply level 3 since they have a land link to Oslo, Bergen or Trondheim (all port cities).

Blue circle is used to show that the submarine is hidden.