Can't tell you which is which, but should be 2 grey water and one black water.
Suggest you get a bucket and open a valve SLOWLY--if nothing comes out, then go in trailer and start running a faucet/shower until you see water at the line. Close and repeat for the other 2. If you happen to get the previous owners black tank contents, close the valve quickly and head to a dump station.
2016 Tiffin 40 QBH
2015 38RSSA, traded
2005 TK3 #1869, 10 yrs of memories,
2017 F450 KR--one more Ford is it
2009 F450 4x4-died; 2010 F450-retired