No, it’s not.
It sounds like you’ve inadvertently set the Default Material Color of edges to grey.
Go to the Styles Browser and set the Edge Color to All Same and Choose Color to black.
That sets the Default Material color of edges to black.
Now go back and change the Edge Color to By Material.
The result is:
• Edges which bear the Default Material (I.e. The edges you have not painted) display as black.
• Edges you paint bear the material color you apply.