Hello, could somebody tell me about the required inserts for Campagnolo's Syncros 2 levers?

I bought a set of Syncros 2 levers that have a 6 speed insert, however I'm looking to upgrade this to a 7 speed (or 8sp if possible) system. I plan to use a Campy Freewheel.

A Fellow BF member has offered to obtain the require insert for me, but I know nothing about what I need or which color would be the right one.

Is there a chart/table available that may show what the various options, compatibility of these inserts in respect to the color?

Thanks!