green bowel movements!

We have started to wean our son, at first he had baby rice for 2 weeks which wasn't a problem. But then we've moved on to banana porridge (which he loves) he's been on it nearly a week now and past couple of days his poo's have been green? .. is it just his body adjusting to different flavours or do I stop it completely? He isn't pained or blocked up it's just literally a change of colour in his poo's