I'm interested in this one....
The "core" WR star, HD 50896 is classified as a WN4-s star.
Normally these Nitrogen WR have no Oxygen emissions, basically Helium and Nitrogen.
The strong HeII at 6560A is commonly mis-identified as Ha.
The strong line at 4686A contributes to a green colour....
(See Richard Walker's Spectral atlas, p28-30)
http://www.ursusmajor.ch/astrospektr...age/index.html
-down the bottom rhs for the English version....