One hundred observers identified by name fifty blue, green, white, and purple test colors. Small areas and low illuminances were used to simulate conditions under which signal lights must be recognized. The results are expressed as chromaticity zones within which the test colors were assigned a given color name with various degrees of certainty. Large individual differences in color naming were found. Variability due to intensity and viewing distance is also demonstrated. The data can be applied to the specification of boundaries for colored signals.
RITA M. HALSEY, "Identification of Signal Lights. I. Blue, Green, White, and Purple," J. Opt. Soc. Am. 49, 45-55 (1959)