These lovely Greek airmail stamps from 1926 are among my favorites.
The light pastel watercolor wash gives them a soft glow that is unlike any other stamps I have seen.
From a Linns magazine article comes the following information:
Greece joined the world of airmail in 1926 under the auspices of a company called Aero Espresso Italiana S.A., underwritten by the Italian government.
The initial Italy-Greece-Turkey air route began Aug. 1, 1926, as a loop of some 870 miles, starting in Brindisi with stops near Athens and Constantinople.
The aircraft were Savoia-Marchetti S-55 double-hulled flying boats, which figured in the designs of the first Greek airmail stamps (Scott C1-C4).
The stamps were not issued until Oct. 20, so the earlier flights used ordinary Greek stamps or Italian airmail issues.
The set of four stamps was designed under Aero Espresso Italiana supervision, approved by Greek postal officials and printed in Milan by Bestetti & Tumminelli, an art publisher of high-quality books. The artist’s name is cited variously in the literature as A. Gavallas, Gravalas, M. Gavalla or M. Gavalas.
The stamps’ artistic style owed more to colorful contemporary advertising labels than to postal issues of the time, which tended to be engraved and single-color. The lithographic printing process used four colors that give the stamps the lovely appearance of a wash of watercolor on a pencil drawing.
You can read the entire article for more information.