Changing border color in mat-form-field

Question

I am using angular material mat-form-field. I have a dark background, and therefore am trying to change the border of the form-field to white. But I am not able

Answer 1

I had tried many things, finally, I am able to change the bottom line (which we are thinking is a border, which is actually not a border), using this:

::ng-deep.mat-form-field.mat-focused .mat-form-field-ripple{
    background-color: black;
}

That colored line is actually span filled with color! Hope this helps :)