Try Insignia Yellow. The blue fuselages on the between the war planes was Rocket Blue. The red for the stripes on the rudder was also Insignia Red. The blue verticle band on the rudder was, yep, you guessed it, Insignia Blue.

John Miller

Or ...

Chrome yellow .
  The Federal Standards Number is 13538 .
Check out the Federal Standards color reference on-line .

HTH

Not trying to add to the confusion, but there is a valuable reference tool available from Frank Tiano Enterprises at

http://www.franktiano.com/scaleproduct.htm

He has a Military Aircraft Color Guide with color chips for different eras and different nations.  The latest edition of this book are available.

The material contained in this book has been verified as being of acceptable accuracy for the purposes of AMA Scale competition by the AMA Scale Contest Board.

The yellow shown for U.S. Army Air Corps and U.S. Navy/Marines from 1939 to 1945 is called Identification Yellow, Shade 48 with Federal Standard 33538.

If you are lucky enough to ever come across a copy of the Chicago Scalemasters Color guide from the early to mid 70's, buy it whatever the cost.  Or if you have a copy you are willing to sell, let me know. This book also meets the criteria of the AMA Scale Contest Board for color documentation in AMA scale competition.  This provides color chips, matched to FS numbers by country.  For USAAF and USN, WWII, the yellow shown in the FS 33538.

For the earlier aircraft before the "pre WWII" years represented by these color charts, I would go with the reference given by Don Hutchinson.  He is somewhat of an authority on the yellow Stearmans flown before the war.