I think that the color you describe as "light greenish/yellow" is one of the late war sky colors as described by Kenneth A. Merrick & Thomas H. Hitchcock on page 41of their "Official Monogram Painting Guide To German Aircraft 1935-1945". There is a greenish-blueish-yellowish color chip, among others, that they call Green-Blue (Grunblau). There is no RLM number assigned to this shade and here is what they say about it:
"During the last months of the war, the Luftwaffe began to employ a new series of sky colors.....The aircraft from which these samples were obtained were varied, but all were operational during the last months of the war. Some sources dismiss these colors as oxidized or chemically altered Light Blue 65 or 76. Thorough analysis of our genuine samples conclusively rules this explanation invalid. Could these colors have been local mixes....? The possibility exists, but the frequency with which the colors have been recorded would rule against this explanation. Therefore, pending official confirmation, we are left with the conclusion that these so-called sky colors were quite intentionally employed by the industry and were quite distinct from previous under-surface colors."
I don't think that you will find a model paint in Green-Blue.
My Mark 1 Eyeball tells me that it is close to FS 34583 with Green-Blue being slightly paler. Another possibility would be the IJAAF Pale Gray-Green used on the undersides of many Japanese Army aircraft. Tamiya makes this color as J.A. Grey XF-14. Again, Green-Blue is paler.
I hope this is of some help and doesn't just confuse the issue.
Pete