Buttons, shadows…If you are using a default application style, a default plasma style, some default color scheme and default window decorations, there’s no such thing that “generates” neon whatever buttons or shadows. The only thing that could define a colored shadow is in the window decorator. You’re saying that you use Breeze, well, than you changed the shadowcolor.
Then you mentioned “buttons”. What buttons? If it’s the buttons on the titlebar, than you are not using a default window decoration.
By “taskbar”, I assume you mean panel? If so, yet again, you’re not using, as you claim, Breeze dark.
There’s no point in deleting your color schemes since, as you claim, you’re using classic.
This is what, according to your settings, it should look like
This is the same, but with non-default color shadows in Breeze window decoration
