It certainly looks like oil. The only two places oil and coolant could realistically get mixed up are at the head gasket and at the water pump.

What's the oil level like? Has it gone down by the same amount as the coolant has gone up? What does the oil colour/texture look like?

Is there anything leaking out of the drain hole on the underside of the water pump housing - either oil, water or both?

However...

So I'd take it straight back to the dealer and let them work it out!

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