Have a look at an xml in the drawable folder called quantum_launchscreen_youtube_prototype.xml, it should be set in there as @ android:color/white so just change that.
You need to change the colour, change the @ color/background_floating_material_dark to something like #cc000000 or something like a translucent black.
Thank you for the response. I have changed to a transparent hex color and still solid black. I even tried pure alpha and still black. I changed it to a solid red to make sure it was the right one and it changed to red.