If for any reason you want a different background as you make your Svelvet visulization there is a built in declaration available. Simply declare a bgColor and set it equal to a string as seen in the example below and the display will update it accordingly.

Background Color

Look at the bottom with the Svelvet declaration and you'll see a property called bgColor set equal to 'pink'. To make the background whatever CSS color you want you merely need to just put in your new string whether it be hexadecimal or string colors.