1992 Mercedes 300D

When I drive the car, park, and then see beneath the car,
I find liquid on the ground.

The location: below a little front from the auto gear stick.

Due to the location of the drop, I suspected transmission leak. So I put napkins on the ground.

The napkins looked wet with transparent liquid (plus dirt on the ground), not pinky liquid (transmission fluid is pinky).

Is something wrong, or is this liquid drop normal?