The red lines represent Troika loans. These cost L+300 or 4% currently and are about 75 billion Euro.
Virtually all of the rest of the debt is held by the ECB or EIB or some other non private entity. Those bonds have an average coupon of around 5%.
If Greece was to leave the Euro, there is no way they can pay these bonds back in Euros. Just redenominating these bonds into Drachma would be a big loss for the Troika. Just redenominating might not even be enough. They might need to default altogether to have a country that can function post default.
The ECB, IMF, and anyone else who has lent to Greece had better seriously consider the ramifications of Greece leaving and how they will deal with redomination or default.
Having the EFSF pick up the losses, which I believe is a consideration, is not a good idea, as it will eliminate any shred of doubt that the whole system in Europe is now a ponzi scheme. As impotent as a Greek IOU may be, at least it maintains the facade that the system isn’t completely broken, but the EFSF directly paying back the ECB and IMF in whole, and receiving nothing but defaulted claims or drachma bonds will be a scam too far.