If you have been wanting to change the default unity background and background color but don't know how here is a simple way to get the job done. This is the color and images that displays before the fade in of your desktop background.

The information I'm sharing came from this link.

Change #000000 to the color of your choice.

sudo -i
xhost +SI:localuser:lightdm
su lightdm -s /bin/bash
gsettings set com.canonical.unity-greeter background-color ‘#000000’
gsettings set com.canonical.unity-greeter background ‘/path/to/wallpaper.png’
You can follow the same procedure for gsettings to change all settings located in com -> canonical -> unity-greeter in dconf.