Coolant - Don't know what's in my Boxster

[Chboro]

I'm going on ownership now for 2 years. Sure I've checked the coolant level and it's always been right at the min mark. And it appears to be yellowish/green. I'm in AZ and it has always run at the proper temp. Right around 190. Even when it's over 100 outside. Recently had my clutch done by an Indy and on the way home the coolant warning light was flashing. Stopped just about when I got home. Coolant level was not at the Min mark anymore. Now, I'm at the delimma of not knowing what coolant is really in my Boxster to top it off. Should I top it off with the yellow/green coolant type or take it in and get the system flushed and the proper coolant put in?