I have 2 backup volumes linked to my iMac. Usually they are both coloured yellow on my desktop but I have noticed one now has changed to green. What does this mean?
Because Time Machine volumes have a separate icon. The green one is your currently active Time Machine volume, the orange one is a regular external volume with no particular significance to macOS.
They do as soon as the system identifies them as currently active Time Machine volume. In other words: they're orange when first plugged in but change to green once they've been properly identified, which usually takes a few minutes.
They do as soon as the system identifies them as currently active Time Machine volume. In other words: they're orange when first plugged in but change to green once they've been properly identified, which usually takes a few minutes.
Not always. I have a Time Capsule always connected and an external disk that I connect weekly. The latter always had the generic orange icon until I manually copied the green one.