I am now in the same situation as our friend Tichus2009: I do not understand how this whole thing works.
So, let's try to see what I m doing wrong:
-First, I installed Facepainter (thanks again for the link)
-Then I loaded a random stl file for testing purposes
-After that, I selected the color number one and painted the whole object
-Then I selected color number 2 and painted the "8mm" text
Like so:

- Facepainter.png (134.96 KiB) Viewed 7839 times
After this, I saved the stl file. So far I believe it's correct, right?
Then, I opened the stl file into Kisslicer.
Finally, I pressed the slice button and changed the appearance so it shows Model+paths.
Here is what the 8mm text zone paths look like:

- KISSlicer.png (56.57 KiB) Viewed 7839 times
What I do not understand is that I only see one continuous path all over. It doesn't look like there is any material change whatsoever, at least it doesn't seem to display any.
So now I'm wondering, is it normal? Let's say I save this as a gcode file and hit print, will there actually be a color change?
Did I do something wrong?
It would be nice if there were at least some kind of basic desciption of the whole process, I tried to search for it but didn't find any explanation, the only information that seems to be available on google comes from this very thread.