How to change Angular 5 Material input placeholder?

In the last version of angular you can remove the placeholder in the input and add a mat-placeholder in the mat-form-field and custom the css with a class

html :

<mat-form-field>
    <input matInput type="text">
    <mat-placeholder class="placeholder">Search</mat-placeholder>
</mat-form-field>

css:

.mat-focused .placeholder {
    color: #00D318;
}

To change the color of placeholder, override the color property of .mat-form-field-placeholder like:

::ng-deep .mat-form-field-placeholder{

  color:red;
}

::ng-deep .mat-focused .mat-form-field-placeholder{

  color:red;
}

To change the color of underline:

::ng-deep .mat-form-field-underline .mat-form-field-ripple{

  background-color:red;
}

::ng-deep .mat-form-field-underline{

  background-color:red;
}

This works perfect. Demo: https://plnkr.co/edit/yF4kXJ500YzefLOnLKNe?p=preview