I am very curious about this question and I did a little test.
I am not sure that what I observed was correct or not, but I checked it many times and got the same result.
Output:
I noticed that when you debug the code and the variable that the pop-up screen appears on, if it is still in use, I mean that having this variable is more important for the compiler than when displaying black text . But after the value of this variable is no longer required by the compiler, blue text will be displayed.
Example:
In the above image variable, fileName used in the second line (it is not visible because the pop-up screen overlaps it, you can see it in the next image) using the string variable, so the text here is black. But see the following image
Here you can see that the fileName variable fileName no longer used, and the debug pointer is at the end of the method. So the text turns blue.
Even in the console window, the text changes depending on the existence of the variable.
Link to the console screen of the first image:
Link to the second screen of the image console:
