8 months old baby green stools when had banana?

My son always has green stoold when he has bananas,I feed him mashed banana for dinner almost everyday and has green stoold,but otherwise he has yellow colour stools only,what could be the reason,is he allergic to banana or is it something else?I stopped feeding him bananas for 2 days and he has normal yellow colour stools,so what coudl be the reason,should I stop feeding him bananas?

 

Yes I tried banana again and yes he has green stools again,so I am planning to stop it.Any idea to make him eat rice,he totally dislikes rice,he makes a vomitting like face and does not take even a spoon,he is 8 months and is still on fruits and veggies alone,any input would be great,he had indigestion with wheat so cant give wheat too,somewhat wlill have to make him eat rice,he is weighing 9.1 kgs,good weight for a 8 month old but he needs carbs too right so frustrated from trying rice in various forms like pressure cooked,strained,etc for him,but still dislikes rice.