I got a fast email from a sister in Christ. She sent the information in answer to my question about "feeling blue".
She and I share children. Her son is married to my daughter!
Thank you, thank you!
Here is what it said.
"If you are sad and describe yourself as "feeling blue," you are using a phrase coined from a custom among many old deepwater sailing ships. If the ship lost the captain or any of the officers during its voyage, she would fly blue flags and have a blue band painted along her entire hull when returning to home port."
It is from a Navy term site. Interesting!