Shine on you is Better than Blue: It was first published in Xun Zi's Persuasion. Xunzi used indigo as a metaphor for a rising star who made academic achievements, and blue grass as a metaphor for their teachers or predecessors.
Cyan: indigo, cyan pigment. Blue: Polygonum cuspidatum, a kind of grass that can extract pigment. Indigo is extracted from Polygonum cuspidatum, but its color is darker than Polygonum cuspidatum.
Metaphor means that people can be improved through study or education. It is often used to indicate that students surpass teachers or that future generations surpass predecessors.