Notification icons colored

Hi everyone,
I’d like to set colored notification icons but I don’t understand how create compatible icons with android platform.

I added to my config.xml file the list of notification icons:

<resource-file src="resources/android/notification-icons/mipmap-mdpi/ic_launcher.png" target="app/src/main/res/drawable-mdpi/ic_stat_onesignal_default.png" />
<resource-file src="resources/android/notification-icons/mipmap-hdpi/ic_launcher.png" target="app/src/main/res/drawable-hdpi/ic_stat_onesignal_default.png" />
<resource-file src="resources/android/notification-icons/mipmap-xhdpi/ic_launcher.png" target="app/src/main/res/drawable-xhdpi/ic_stat_onesignal_default.png" />
<resource-file src="resources/android/notification-icons/mipmap-xxhdpi/ic_launcher.png" target="app/src/main/res/drawable-xxhdpi/ic_stat_onesignal_default.png" />
<resource-file src="resources/android/notification-icons/mipmap-xxxhdpi/ic_launcher.png" target="app/src/main/res/drawable-xxxhdpi/ic_stat_onesignal_default.png" />

I generated the icons with Android tool: http://romannurik.github.io/AndroidAssetStudio/icons-notification.html

But my icons are trasparent and white color.

The icons are correctly showed into my notification area but I’d like to create blue icons, not white. If I create custom icon using other tool (example photoshop), the icon not showen (only grey box)

Thanks in advance for your support

Luca