Estilos para Widgets - Toolbar como exemplo

activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
    android:orientation="vertical"
    android:layout_height="match_parent"
    tools:context=".MainActivityFragment">

    <include layout="@layout/toolbar_main" />

</LinearLayout>

style.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>

    <style name="AppTheme" parent="Theme.AppCompat.Light.NoActionBar">
        <item name="android:windowNoTitle">true</item>
        <!--We will be using the toolbar so no need to show ActionBar-->
        <item name="android:windowActionBar">false</item>

        <!-- Set theme colors from http://www.google.com/design/spec/style/color.html#color-color-palette-->
        <!-- colorPrimary is used for the default action bar background -->

    </style>

    <style name="ToolbarApp">
        <item name="android:background">#336699</item>
    </style>

</resources>

toolbar_main.xml

<android.support.v7.widget.Toolbar
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/toolbar"
android:minHeight="?attr/actionBarSize"
android:layout_width="match_parent"
android:layout_height="wrap_content"
style="@style/ToolbarApp"
    >

    <ImageView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/abc_ic_commit_search_api_mtrl_alpha"
        />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Acesso"
        >

</TextView>

</android.support.v7.widget.Toolbar>