These are the ones I know:

Märklin 60902 (used also in the 60901, 60903 and 60904 conversion sets ):

Red Track power conductor (pick-up shoe)
brown Track ground return (wheels, chassis)(NOT decoder ground!)
gray Hot wire (-) to front headlight
yellow Hot wire (-) to rear headlight
blue Motor connection
green Motor connection
orange Function return (+)
brown/red Hot wire (-) to function 1
brown/green Hot wire (-) to function 2
violet Decoder ground

ESU LokPilot:

red Track power conductor (pick-up shoe)
black Track ground return (wheels, chassis)(NOT decoder ground!)
white Hot wire (-) to front headlight
yellow Hot wire (-) to rear headlight
orange Motor connection
gray Motor connection
blue Function return (+)
green Hot wire (-) to function 1
violet Hot wire (-) to function 2

Märklin 6603 (old Delta decoder):

Red Track power conductor (pick-up shoe)
brown Track ground return (wheels, chassis)(NOT decoder ground!)
gray Hot wire (-) to front headlight
yellow Hot wire (-) to rear headlight
blue Motor connection to field coil
green Motor connection to field coil
black Motor connection to armature

OK, I'll bite...
What is the difference between the 60902 Blue and Green motor wire, and the Delta blue, green and black? If I have a Delta Lok, what does the black connect to?

I have a Delta OBB 1022 (the Orange one). What paarts would I need to order to convert to digital? I have a 39222 (green) that runs like a champ, and I would like both to run the same.

What perz means is that a DC motor only needs + and - voltage to work, hence the blue & green wires from the 6090x decoders since the rotor lives in a permanent magnet field. Either ou go one way or the or the other depending on what wire is fed with voltage/current. The conventional Märklin motor has 2 coils in the stator that need to be "energized" with current/voltage to become magnetic... These 2 coils are in one end connected together, giving a reference point to "common" electrically... This means that the green would activate one of the stator coils to "simulate" a permanent magnet and "energize" the motor to move in one direction, and the blue would "energize" the other coil so the motor moves in the opposite direction. The "common" is the black wire, aka the "center" tap where the coils are connected together in one end. Since the Delta is made to work with the so called "AC" motors with those 2 coils and a reference point, it just has to have that black wire as a reference point.

Your could see it as the Delta (and c80) tries to make a permanent magnet motor out of the standard dual-electromagnet motor, hence the polarity of the wires and the need for a "common" point (ze schwartze wire)... It is actually kind of like how M turnouts work, activate one coil - the turnout moves in one direction, activate the other - it moves in the other direction.... The visual difference is that the loco motor stator coil seems to be "one coil" - when it in fact has 2 separate coils...

Sorry if I sound "blurry"... [:p]