Create a custom style which uses @android:style/TextAppearance as parent in your styles.xml file:
<style name="error_appearance" parent="@android:style/TextAppearance">
<item name="android:textColor">@color/red_500</item>
<item name="android:textSize">12sp</item>
</style>
And use it in your TextInputLayout widget:
<android.support.design.widget.TextInputLayout
android:id="@+id/emailInputLayout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:errorTextAppearance="@style/error_appearance">

Edit: Set the hint on the object, which is inside your TextInputLayout (EditText, TextView, etc.) to hold different colors for the hint and the error.