When Profile View Menu Style is set to Tiles, this value will set the default background color for tiles in this view. Note that individual Profiles can override by setting a color for their Tile background when presented in the View Menu.
This setting uses your Web Browser's Color editor - if you use IE11 instead of an HTML5 Browser like Edge or Chrome, an in-page editor is used.
Here is an example of editing with the Edge Color Editor:
