Passenger footwell leak, oil?

Orange red usually indicates coolant The drain from the air conditioner generally will be just clear water.

 

Pretty much I think the only thing you're going to find in that area is a heater core that's inside the box with the AC evaporator would have to be a pretty good size leak to fill up that box and get to the floor maybe somebody just spilled some Fanta

 

You can check the power cell, coolant, and transmission fluid to see where the leak is occurring.

 

Put your finger in the leak and bring your finger to your nose what do you smell coolant is distinctive oil is pretty distinctive how it's going to get on the floor of the car not likely. So again your choices are water from the condensate drain of the AC which is possible and it used to be if your heater core had a leak You could get same red Asian coolant on the floor I'm not sure if this can happen in the Prius or not they've changed a lot of these heater core locations and things around so that the core stays closer to the firewall and the connections are actually kind of sticking through the firewall and if the thing leaks it'll run down the firewall more than it will in the car so there should be a smell if it's serious if it's condensate drain it's not really that serious it doesn't do well to keep your car cool so you may want to run a small plastic rod through the firewall penetrating drain hole and when you pull the little rod out there's a whole bunch of water come out You just found your problem probably.