See att' grass on the lawn has about 1.5 inches of brown topped with green shoots.

How do you get it green all the way down or is that not possible?

Try de-thatching. https://www.youtube.com/watch?v=TIjPMtgE5F8

And fertilizing. Try Ammonium Sulfate 21-0-0 at 5 kilos per 100 sq meters of grass surface. Spread evenly and water in.  Mow weekly at 2 to 3 inches height.

When I look closely at the grass after watching the vids it looks to me like a different problem. The grass seems to grow as a brown shoot then 3 or 4 green blades grow from the top of that shoot.

Basically each grass growth, say that with a lisp, sorry, is 50/50 brown/green.