I have a (dull) theory about engine effects (partially sounds) and fuel usage, let me introduce it:
Rheinland (Green with smoke) - Plutonium-MOX mix, ratio 1:3
Liberty (Silver with rings) - H-fuel-MOX mix, 3:1
Bretonia (Blue) - MOX-H-fuel mix, 3:2
Kusari (Yellow fire) - Pure H-fuel
Civilian (Like Liberty, but different sound) - H-fuel-Deuterium mix, 4:1
Borderworld (Like Liberty, but with different sound) - H-fuel-Deuterium mix, 3:1
Order/Pirate/Corsair (Same sound as BW, but with red, bunsen burner like flame) - MOX-Deuterium mix, 4:3
Civilian Capital Ships (Yellow-blue) - MOX-H-fuel mix, 3:5
Yeah, the theory is like I said very dull, and is just in its first stages. Feedback is appreciated.