How do I change md-input-container placeholder color using css in angular material?

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;
}

Placeholder is depicted as a <label> in Angular Material. So you actually need to style the label not the placeholder.

As soon as you click (focus) on the input this <label> which is looking as a placeholder slides up and converted into a form <label>.

So you just need to apply this CSS:

/* When the input is not focused */
md-input-container label {
  color: red;
}

/* When the input is focused */
md-input-container.md-input-focused label {
  color: blue;
}

Have a look at this Plunkr Demo.

In Angular 4+

First you will need to turn ViewEncapsulation off to style Material Elements. Be warned this is subverting the Angular emulated-shadow DOM default and you should proceed with caution (https://blog.thoughtram.io/angular/2015/06/29/shadow-dom-strategies-in-angular2.html).

In dummy.component.ts:

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

Then give your < mat-form-field > element a unique class in dummy.component.html:

<mat-form-field class="dummy-input-field" floatPlaceholder="always">
  <input placeholder="Dummy"/>
</mat-form-field>

Finally in dummy.component.css apply the styling:

.dummy-input-field .mat-input-placeholder {
  color: red;
}

Similarly, if you'd like to dynamically change color if the field is focused:

.dummy-input-field.mat-focused .mat-input-placeholder {
  color: red;
}