Inconsistent app colors on Marshmallow recents screen

Question

Device

Nexus 6 running 6.0.1.

Context

I have an app in which the Toolbar and content areas share a background color:

If I hit the 'recents' button, this color matching is preserved in the recents UI for my app:

If I select another app (in this example, the Project Fi app) from my recents screen, then hit the 'recents' button again, this color matching is no longer preserved:

This appears to happen regardless of:

1. whether or not I explicitly apply a TaskDescription using Activity.setTaskDescription;
2. whether I use the window or the root RelativeLayout to set the background color of the content area.

On Nougat, the color matching is preserved at all times on the recents screen (Nexus 6 running 7.0):

Questions

• Is this expected behavior?
• Is there a way to keep these colors matching on Marshmallow?

Relevant Files

build.gradle

apply plugin: 'com.android.application'

android {
    compileSdkVersion 24
    buildToolsVersion "24.0.0"

    defaultConfig {
        minSdkVersion 21
        targetSdkVersion 24
        //...
    }
}

dependencies {
    compile 'com.android.support:appcompat-v7:24.0.0'
}

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
          package="com.github.stkent.recenttaskuicolortest">

    <application
        ...
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

styles.xml

<resources>

    <style name="AppTheme" parent="Theme.AppCompat.Light.NoActionBar">
        <item name="colorPrimary">@color/colorPrimary</item>
        <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
        <item name="colorAccent">@color/colorAccent</item>
        <item name="android:windowBackground">@color/colorPrimary</item>
    </style>

</resources>

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="@dimen/activity_margin">

    <android.support.v7.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/toolbar"
        android:text="Hello World!"
        android:textColor="@android:color/white" />

</RelativeLayout>

MainActivity.java, version 1

package com.github.stkent.recenttaskuicolortest;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        final Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        getSupportActionBar().setTitle(R.string.app_name);
    }

}

MainActivity.java, version 2

package com.github.stkent.recenttaskuicolortest;

import android.app.ActivityManager;
import android.os.Bundle;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        final Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        getSupportActionBar().setTitle(R.string.app_name);

        updateRecentTasksUi();
    }

    @Override
    protected void onResume() {
        super.onResume();
        updateRecentTasksUi();
    }

    @Override
    protected void onPause() {
        updateRecentTasksUi();
        super.onPause();
    }

    private void updateRecentTasksUi() {
        final ActivityManager.TaskDescription taskDescription =
                new ActivityManager.TaskDescription(
                        getString(R.string.app_name),
                        null,
                        ContextCompat.getColor(this, R.color.colorPrimary));

        setTaskDescription(taskDescription);
    }

}