[Aloisius]

How green an orange is when ripe has to do with the climate they are grown in. In warm climates with little variation in temperature between day or night, oranges will remain green on the tree even when ripe. If nights get cold enough (~55 F), they will turn orange.

That said, in the US, oranges destined for markets de-greened for aesthetic purposes since customers won't generally buy them otherwise.

[lightedman]

"How green an orange is when ripe has to do with the climate they are grown in."

Not true for all cultivars. For example, the emerald orange rind always looks like a lime.

[Aloisius]

I'm not familiar with that one and can't seem to find it online. Do you have a link?

Limes will actually turn yellow when ripe. We just pick them early.

[lightedman]

https://i.imgur.com/gX7RCKs.jpeg

Sometimes they'll go orange in the rind but most times they stay green like a lime.

[Aloisius]

Those look like calamondins (Calamansi limes).

Just like with oranges, their skin will remain green or mostly green unless grown where it gets cold enough, then their skin will turn yellow then orange then reddish orange. Where I live, calamondins trees have entirely orange fruit when ripe.

[lightedman]

They look like them but taste much closer to a mandarin!