print 'NA' for color if photo reports a negative flux
print 'NA' for color if photo reports a negative flux

jeff-regier/Celeste.jl,jeff-regier/Celeste.jl,rgiordan/SloanDigitalSkySurvey.jl,tkelman/SloanDigitalSkySurvey.jl,jeff-regier/Celeste.jl,JuliaPackageMirrors/SloanDigitalSkySurvey.jl