The Boeing P-26A was an early monoplane fighter for the USAAF and proved popular because of its aerobatic qualities. Boeing created an export version of the P-26 called the Model 281 and its through this designation that a single plane (a demonstrator) made its way to Spain and consequently ended up fighting for the republicans in the air battles of the Spanish Civil War. It was later shot down in 1938 and compensation was paid to the Boeing company after the war.
There are only a few photos of the Model 281 which made it to Spain and these seem to show it painted with an olive drab fuselage and yellow wings, the pictures were taken in 1935 before the conflict and show large lettering on the wings and tail (NR12775) as well as the Boeing logo on the tail.
(Picture from the archives of Juan Arráez)
This picture could have been taken in the US before shipping or in Spain it is unclear.
The next picture has been positively identified as being in Spain in 1935, however the colour of the aircraft is a little unclear and the picture could have also been re-touched.
(Published in the May 1935 issue of Revista de Aeronáutica (Aviation Magazine))
There is a picture that is widely seen in modeling world of the 281 in Spain which shows an attractive bare metal finish with the republican red band on the fuselage and wing tips with the red, yellow and violet on insignia on the tail.
However I’m not sure it would have ever looked like like this and I think the most likely rendition of the 281 is this drawing:
Model kits available: P-26 Models Scalemates