2019 Ford Ranger small red puddle under front

Yes, red and oily is almost certainly transmission fluid. Your Ranger has electric power steering, so there is no power steering fluid to confuse it with, and Ford coolant is orange, not red. The 2019 Ranger runs the 10R80 10-speed automatic, which uses Motorcraft Mercon ULV fluid.

Where to look: the transmission cooler lines run from the transmission up to a cooler at the front of the truck, and that run is the most common leak point on these. Check the junctions where the hard lines meet the rubber hose sections, the fittings where the lines connect to the cooler, and the cooler itself for wetness. A puddle under the front usually means a line fitting or the cooler, not the transmission itself, which sits farther back. The pan gasket and the input and output seals can leak too, but those drip mid truck, not up front.

One important note: the 10R80 has no dipstick. Checking the fluid level is a plug procedure done with the transmission warm on a lift, so get the leak source found and fixed soon. Running low on fluid burns the clutches fast, and a small puddle today turns into a tow bill next week.