Memories of green

I've been looking for the meaning of this expression for quite some time, and haven't been able to find it.

I think it's kind of poetic, but I'm not sure...

[Tdol]

I thought it just meant when things were young- we use 'green' for youth, like the wood of a young tree.

And 'memories of blue'? Would it mean something like 'sad memories'?

The construction "memories of green" instead of "green memories", or something like that, seems odd to me, so that's why I thought it would be something like an unusual expression...

[Tdol]

We often say 'memories of...'. It doesn't strike me as an unusual structure with 'memories':
childhood memories
memories of childhood

Both are fine to me.