Angular Material card shadow colour

Adding the following to your CSS will change the box-shadow for the mat-card

.mat-card:not([class*=mat-elevation-z]) {
    box-shadow: 0 2px 1px -1px rgba(0,0,0,1), 
                0 1px 1px 0 rgba(0,0,0,1), 
                0 1px 3px 0 rgba(0,0,0,1);
}

If you are using an elevation, of course this CSS will need to be modified a bit.

Stackblitz

https://stackblitz.com/edit/angular-yxb2ow?embed=1&file=app/card-overview-example.css