If it's black it's your rear main seal unless the oil pressure sender, intake gasket or valve cover are leaking bad enough to run down there.
If it's reddish the front seal of the trans is leaking. To repair either the trans has to be pulled and if it's the rear main the oil pan also which in a 2wd means pulling the engine.
I'd thoroughly clean the engine first to be sure it isn't one of the upper things running down. They're all easy by comparison. Hard to tell in the pic because that area is pretty oily and dirty.They're all easy by comparison.
I also can't figure out why the oil filter appears to be on the passengers side next to the transmission cooling lines.