A few questions about the meaning of ‘light turns copper in the spray’

A few questions about the meaning of ‘light turns copper in the spray’

The passage below is from Fathoms: The World in the Whale Hardcover by Rebecca Giggs.

The sun drags its fingers along ferrous runnels in the sand. Soon it will be too dim to take good pictures. The race is on. I push closer to our immense animal interloper, and, though the crowd still obscures it, I can begin to see it, in parts, between people. The leaving light turns copper in the spray. Like a glowing periscope, the boys’ tablet allows those behind them to see a little further ahead: they hold it up. Floodlights are being assembled to afford a greater opportunity to observe the whale and take its mortuary portraits.

The author tries to get closer to see a stranded whale in an ocean bath.

My questions are about the bold-faced sentence.

First, on ‘leaving light’ seems to mean ‘setting sun’.

Am I right?

Second, what does ‘light turns copper’ mean? ‘Copper’ means ‘sort of metal’, but that doen’t help.

Third, the meaning of ‘spray’. To me it means ‘mist of water’. But in this context I’m not sure.

Last and foremost, I cannot comprehend the whole sentence.

The leaving light turns copper in the spray.

Thanks in advance.