Aiming point on target

[joho]

Hi
I have this graphical sheet over targets weakspots (made by Augie, Nemesis and Dietrich) where color green represent propeller and red ammunition hold.
Then there is yellow wich I belive is engineroom, orange oiltank but Im not sure wich is wich. Finaly a purple coloration stechin over the main center part of targets.
If you now the sheet and the meaning of the colors please illuminate me.

Now I have been aiming for the yellow and orange parts on a majority of targets beneth the brige but it dont seem to do as much damage as when I aim for the cargo hold in front or aft of the bridge. Wich is not marked on the sheet I have.
Is it like so that you are NOT supposed to aim for these parts.

WHERE DO YOU AIM at a cargo ships C2, C3, Merchant or likewise.
Tankers and naval vessels are a bit easier the question does not apply to them.

The sheet I am refering to comes rom 3rdflotilla.org.