How can you feel blue?

Everyone understands but no one sees it :-)
The expression knows many groundings like it seems to be the colour of mourning in some African cultures, it also could come from the Greeks and their cyan god.
So which one is true? I honestly have no idea, but we all know what we mean when we say I feel blue.

As people know I see all people in colours, or rather I feel people their colours, like to feel is maybe better because I always have to presume and not knowing for sure.
Even for my self, I would have to hear them speak and see their behaviour, and most of all let me feel your texture.
But still..... I feel colours in people.
A blue person in my context would be a fairly intelligent person, the next I search is how is it with your yellow?

how green can you get, for yellow is colour of hope and wish, the more I feel that the more I know, this also can be dreamers, not always taking life in their own hands.

When the blue gets to the purple, it is a different story, they have the power to act for there selves, and take the matter in own hands.

When you get a light blue, you feel in harmony with your self you can take on what you want, the next colour coming in will be what you are going to do with the harmony and I can take on everything?
Do you do nothing you will get more yellow ... * So that is how* I feel a colour in people.

But where comes feeling blue come from?
The nicest story and I believe the most is the ship loosing its captain, and they have to thrust the body to the deep blue sea.
They will sail back with a blue edge on their flag, or even a blue flag. The whole ship is in mourning, the whole crew is grieving for its loss, they all feel blue, the colour they saw taking possession of their captain.
*Touching is it not?