When observing Alnitak zeta Orionis recently, I noticed that one side of it appears creamy yellow and the other side blue.
Increasing magnification split the stars into a double consisting of a blue white with a yellow companion.
The main star is listed as a class O with the companion being a B2 III. Neither of these stars are yellow so what is giving the yellow appearance?
Unfortunately I am unable to image this but wondered if someone could explain what I am seeing.