Catch, the Franklin was initially painted in camouflage measure 32/6A which changed to 32/6A-3A when the port side was repainted making her the only carrier to be painted with 2 different designs, during this period up to Dec 44 she used Flight Deck stain 21. In Jan 45 the flight deck continued to be No.21 while the primary Camo was repainted to measure 21 consisting of navy Blue (5-N) on all vertical surfaces.
Now from looking at various sources and to keep it simple, given your paint sources I would suggest Tamiya XF-18 Medium Blue as Flight deck stain 21.
Paint your deck straight out of the bottle, then add a small amount of white to lighten it and mist it on in a cloudy type irregular pattern to help simulate weathering, this should be followed by some light dry brushing as well.
Now this is not a perfect match but it wil give you a reasonable facsimile of what you are after, I think!
It is certainly what I will be trying when I get to the painting stage of my USS Essex (CV-9)
Now Deck Blue 20-B revised is a Dark Blue colour and I will also be trying this as well on other US carriers using XF-50 Field Blue with white and black added to create the deck colour with dry brushing of the lighter variation also.
You could also try to get hold of the White Ensign Enamels for the 2 colours which are correctly matched to the proper US colours, these are,
US 11 Flight Deck Stain 21
US 10 Revised Deck Blue 20-B
Hope this helps...
Oh, and Wasp also used Flight Deck Stain 21, and using Camo design 33/10A