To customize tool bar style, first create tool bar custom style inheriting Widget.AppCompat.Toolbar, override properties and then add it to custom app theme as shown below, see http://www.zoftino.com/android-toolbar-tutorial for more information tool bar and styles.
<style name="MyAppTheme" parent="Theme.AppCompat.Light.NoActionBar">
<item name="colorPrimary">@color/colorPrimary</item>
<item name="colorPrimaryDark">@color/colorPrimaryDark</item>
<item name="toolbarStyle">@style/MyToolBarStyle</item>
</style>
<style name="MyToolBarStyle" parent="Widget.AppCompat.Toolbar">
<item name="android:background">#80deea</item>
<item name="titleTextAppearance">@style/MyTitleTextAppearance</item>
<item name="subtitleTextAppearance">@style/MySubTitleTextAppearance</item>
</style>
<style name="MyTitleTextAppearance" parent="TextAppearance.Widget.AppCompat.Toolbar.Title">
<item name="android:textSize">35dp</item>
<item name="android:textColor">#ff3d00</item>
</style>
<style name="MySubTitleTextAppearance" parent="TextAppearance.Widget.AppCompat.Toolbar.Subtitle">
<item name="android:textSize">30dp</item>
<item name="android:textColor">#1976d2</item>
</style>