At this point, since the OP is refilling with coolant continuously, I wouldn't worry about the colour of the replacement coolant. Leak appears to be at the hose at the expansion tank or the expansion tank itself. BTW, there are many compatible coolants which are not blue, which is what the OP is probably using. Any NAP free OAT coolant that meets ASTM D-3306 will do. Mine happens to be green. Also, all modern coolants that aren't water are synthetic.

 

I would start with removing the hose from the tank and looking for cracks around the part that sticks out, then check the condition of the “o” ring inside the hose connector. Put some petroleum jelly on the hose connector and make sure it goes back all the way.

 

Drove it again last night and sat there for about 45 minutes after I parked and no leak. I woke up this morning and a larger puddle under my car. It seemed like one of the lower hoses leaked because coolant tank was almost empty. I am making an appointment to take it in. Hopefully it is nothing serious.

 

I found out where mine was leaking using a flexible shaft mirror and flashlight.

 

Get under the car and remove the cover right under the water pump and thermostat (7 screws).

Wipe down the area and make it clean.

Run the car and see where its leaking coolant.

Your mechanic is going to do the same task.

You can do it and might find out all you need to do is tighten a few hose clamps.