Looks like I had green coolant in there but my local auto store only had:
Prestone® MAX European Vehicles (Blue) Antifreeze + Coolant
Am I screwed? Should I drain it ASAP?
Edit: the large tank was basically empty so I doubt any mixed yet but there was still some in the smaller tank
If the blue coolant you bought was a G48 coolant equivalent, then it’s interchangeable and intermixable with HT12 (the green coolant).
See here and here