If your web page's background is neither black nor white, you can set the background colors here to match your web page's background.

Dark logos' background:

White
Custom

Light logos' background:

Black
Custom

To insert an Exhibit logo into your web page, use this code but change the color:

<center ex:role="logo" 
  ex:color="SlateBlue">
</center>
You should see something like this: