What specific coolant did they use to refill the radiator? That is the first thing I would suspect. The toyota coolant (atleast for the IS300) is red maybe orange-ish but to me always looked pink when it dried. If you wanted to confirm you could probably tell just by looking at the color of the coolant or even pull a small sample of it then let it dry and compare color.
Can't think of many other fluids that would be hanging out and settling in that area.
NA Supra Clutch & Flywheel // Dezod Green Headers // BC 264 Cams // Titan V2 Cam Gear // JOEZ Intake