Spanish Civil War Artillery piece colours?

[SJWi]

I'm building a 15mm Nationalist SCW force and have recently bought some of the Irregular Miniatures "useful gun" range to serve as heavy artillery.  Does anyone know the paint scheme in use at the time. I have seen both green and dark gray field pieces but don't know if these are correct as I assume  some the photos are modern colourations of original black and white photos.

Thanks

[Panzer21]

Broadly correct.
It depends where it came from. Most pre-war artillery was in grey.
I doubt there was much time or inclination to repaint artillery supplied from France, Italy, USSR or Germany.....

Neil

[SJWi]

Neil, thanks for the advice.  I will probably use grey as a contrast to the green uniforms.