This technique is crazy! It allows to both:
  • separate gaseous mixtures
  • identify gaseous compounds
You actually see discrete peaks at different minute counts on the other end.
It is based on how much the gas interacts with the column.
Detection is usually done burning the sample to ionize it when it comes out, and then you measure the current produced.
The procedure remind you a bit of gel electrophoresis, except that it is in gaseous phase.
Video 1.
Gas chromatography by Quick Biochemistry Basics (2019)
Source.
Video 2.
How I invented the electron capture detector interview with James Lovelock by Web of Stories (2001)
Source. He mentions how scientists had to make their own tools during the 40s/60s. Then how gas chromatography was invented at the National Institute for Medical Research and gained a Nobel Prize. Lovelock came in improving the detection part of things.
The name makes absolutely no sense in modern terms, as nor colours nor light are used directly in the measurements. It is purely historical.

Articles by others on the same topic (1)