Hi Daniel, 
I had a similar find last year and was advised that the yellowing of the ovary could have been caused by lack of sunlight through emerging bud being covered with moss/ leaves etc. 
In my case this was correct and the ovary changed back to green - although i will be re checking this year. 
Also yellowing can be a sign of disease or fungal issues -- as in bulb in the process of decay -- i also had this with several other possible yellows last year. 
In short as per advice given to me -- keep an eye on it to see for any signs of colour reverting to green -- or bulb dying off, cross your fingers and also prepare yourself for another of lifes potential disappointments 
