Finnish Air force aircraft insignia from 18th of March 1918. 
The Finnish national insignia was born on 2nd March 1918, when the Swedish count Erich von Rosen had painted his good luck emblem, a blue swastika on a white background, on the wings of his Thulin type D (Morane-Saulnier type L) monoplane. Four days later this plane arrived to the army of the white Finland as a donation.  
The contemporary commander of the Air Corps captain Allan Hygerth proposed on 13th march 1918 to the commander in chef of the Army of the republic of Finland, that the aircraft should be marked with the von Rosen swastika sign added with the early state flag. As an appendix was a swastika having the arms 3/16 of its width and red flag in 1:2 proportions with a yellow horizontal bar being 1/4 of the height of the flag and a yellow vertical bar being 1/8 of the length of the flag positioned at 2-3/8 of the length. From preserved aircraft of their parts the colour definition of the blue was darkish in tone and on the US Federal Standard FS 595a (35053) represents a good average. 
On the 18th of march 1918 CIC of the Army general baron Carl Gustaf Emil Mannerheim issued an order Nr. 26 officially approving first Finnish Air force aircraft insignia.
All troops are now informed that our aircraft will use from now on as a recognition mark the following sign (swastika) in blue colour on the wings and fuselage, in addition a red flag with a yellow cross will be attached to the tail. 
Keskinen, K., Stenman, K. &amp; Niska, K. (1996) Suomen ilmavoimien maalaukset ja merkinnat / Finnish Air Force camouflage and markings. Tampere: Apali (ISBN 9525026051)

The hexadecimal color code #263b56 is a dark shade of cyan-blue. In the RGB color model #263b56 is comprised of 14.9% red, 23.14% green and 33.73% blue. In the HSL color space #263b56 has a hue of 213.75 degrees, 38.71% saturation and 24.31% lightness. This color has an approximate wavelength of 485 nm. Federal Standard 35053 is a matching paint color. Encycolorpedia
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Kwasura