[robtek]

As i remember the damage model includes all the fluid filled pipes, glykol/water, fuel, hydraulic fluid, etc...
So lets assume that OM sticks to details and tries to reach perfection, the we can also assume that we will have different smoke/fluid trails from wounded planes.
A cooler leak will doubtless leave a white trail, burning oil a light grey and burning rubber and fuel/oil mix a black trail, each varying according to the amount of damage and or burning material.