Styling mat-form-field input in Angular/Material

For change the styles of material inputs with scss:

Standard:

::ng-deep .mat-form-field {
    .mat-input-element {
        color: slategray;
    }
    .mat-form-field-label {
        color: slategray;
    }
    .mat-form-field-underline {
        background-color: slategray;
    }
    .mat-form-field-ripple {
        background-color: slategray;
    }
    .mat-form-field-required-marker {
        color: slategray;
    }
}

Focused: (when selected)

::ng-deep .mat-form-field.mat-focused {
    .mat-form-field-label {
        color: #ff884d;
    }
    .mat-form-field-ripple {
        background-color: #ff884d;
    }
    .mat-form-field-required-marker {
        color: #ff884d;
    }
    .mat-input-element {
        color: #ff884d;
    }
}

Invalid:

::ng-deep .mat-form-field.mat-form-field-invalid {
    .mat-input-element {
        color: #ff33cc;
    }
    .mat-form-field-label {
        color: #ff33cc;
        .mat-form-field-required-marker {
            color: #ff33cc;
        }
    }
    .mat-form-field-ripple {
        background-color: #ff33cc;
    }
}

DEMO

you can also use ViewEncapsulation.None to avoid ::ng-deep which is deprecated:

import { ViewEncapsulation } from '@angular/core';

@Component({
    ...
    encapsulation: ViewEncapsulation.None
})

From my understanding, both features seem to be in MatFormField.

1. floatPlaceholder is deprecated, because now it's [floatLabel] for FloatLabelType ('never', 'always', 'auto'), applied using input
2. You can change the color of the underline with input [color], however you can only select colors from your theme ('primary', 'accent', 'warn'). For more on how to setup the theme go to their website here,

<form class="search-form">
  <mat-form-field class="example-full-width"
                  floatLabel="never" color="primary">
    <input class="toolbar-search" type="text" matInput placeholder="search">
    <mat-icon matSuffix style="font-size: 1.2em">search</mat-icon>
  </mat-form-field>
</form>

You can use the css selector you use below:

/deep/ .mat-input-underline {
   background-color: white;
}

The /deep/ combinator is slated for deprecation in Angular, so its best to do without it. Unfortunately, the .mat-input-underline from Angular Material is highly specified, which makes it very difficult to override without using /deep/

The best way I have found is to use an ID, which allows you a higher specificity compared to the default Angular Material styles.

 <form id="search-form" [formGroup]="form" (ngSubmit)="submit()">
    <mat-form-field>
      <mat-placeholder class="placeholder">Search</mat-placeholder>
      <input type="text" class="toolbar-search" matInput formControlName="search">
      <mat-icon matSuffix>search</mat-icon>
    </mat-form-field>

Then, your 'search-form' id can be used to target the input. You can't target the mat-form-field-underline in the component.scss without breaking your view encapsulation. It's easier to do this at the global level, by adding this to your global.scss

global.scss:

#search-form {
  .mat-form-field-underline {
    background-color: $accent;
  }
  .mat-form-field-ripple {
    background-color: $accent;
  }
  .placeholder {
    display: none;
  }
}

I hope the Angular Material team pulls back their specificity in the future, because currently there's no easy way to override their defaults.