I believe the black (darker) ones are intake. I remember it being counter-intuitive...seems like it would make more sense to have the exhaust seals in black...but whatever.

If yours don't have the colors, then I guess it doesn't matter? :\

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Current cars:
2000 ML55 AMG, 174k miles
2003 C240 T-Modell, 202k miles
1995 S320, 207k Miles