Visited the Louvre and the George Pompidou museums in Paris, France November 2017. These paintings reminded me of the blue ink used to write during  my school days in the 70s. The kids born after 2000,  have neither seen nor heard, let alone used ink pens. They have no idea about the pen-nibs, the blue stains on our fingers and pockets holding the leaking pens in school uniforms, the various types of pens and their variable costs,  the plain ink pens and the 'fountain pens'. They have no idea of the ink bottles, the 'Camel' company's ink bottles, the rolling of chalk pieces on paper by the students, to absorb the drop of ink which fell from pen to paper...

I recall adding water to my pen to make the ink last when I ran out of ink and the above painting's faded blue is exactly the same shade of the watered down ink in my pen! 
And I also recall my kind-hearted  class-mates who opened their pens and dropped a few precious drops of ink into the empty pens of their classmates who had stopped writing the notes being dictated by the class teacher. 
Some teachers were so bloody punitive,  that, those without ink, went through the 'moves' and pretended to be writing, even when there was no ink in the pens...to avoid punishment for running out of ink!
Some students from 'well to do families' had spare pens to share...in those days. Today pens called 'dotpens' are ubiquitous.