How does overlay work in Canvas?

Question

Canvas

Here is an example - https://jsfiddle.net/SmiteVils/ry6h7kpn/23/. The lines are given a specific color. But when applied, the colors seem to add up. And the more intersections, the brighter the color. And if you draw 20 lines in the same place, then it will be very bold. What kind of behavior? Where to read about it?

Answer 1

https://jsfiddle.net/huhf61Lz/