How to implement a background flow along with an arrow while changing the text color?

Question

css

There is the following menu. It is necessary to implement the filling (overflow) of the next excess when moving from one to another.
And better with an arrow.
An arrow is implemented for each li on after.
Tell me how to do it or maybe examples where it has already been done. The key point is changing the color of the text

Answer 1

Once upon a time I wrote this example to someone.
There are 10 lines of code, if you understand the principle, there will be no problem with a smooth change in text color