Why is my green tea yellow?
Fresh Japanese green tea leaves (even after they're processed) should look green. The Japanese steam the leaves which is why the leaves maintain the green colour. However, you've to keep the green tea dry. If it's exposed for too long (or too often) to air and humidity, the leaves will start to oxidise and turn yellow. In such cases, it also often starts to loose it's aroma and flavour.

I hope this helps!