[Buckeye30]

Neutral Grey would seem odd for undersides being quite dark but at higher altitudes only had a 12% reflectivity (Sky / Sky Type "S" was 43% and White was 75%).
The Air Corps being very though on this subject ran tests in Dec. 39 for "Sky camouflage"; colours tested were Black, Neutral Grey, Light Grey, Dark Blue, Light Blue, White, Light Blue-White pattern and Alclad. Least visible at 5,000ft. was Light Blue, but above 10,000ft. Neutral Grey was best result. Most visible at higher altitudes were Light Blue and White. Obviously why NG was adopted.


Nick