Hey Jim,
I'm no expert, but after a little looking around I found this site,
Grumman F6F Hellcat and
Aircraft illustration
I compared the colours against the paint conversion chart,
The Ultimate Model Paint Conversion Chart
And I think the colours you need are -
val045 US Lt gray, val089 Lt sea blue, and val087 Dark sea blue.
These are colours for WW2 aircraft.
As I said, I'm no expert but I hope this helps.
Tony.