You can adjust the css styles in /components/com_bfauction_plus/css/bfauction_plus.css, however be aware that any changes you make will be overwritten each time you upgrade the software. It may be better to add these styles to your site template. You can use the !important keyword to ensure that your setting is used.
As an example, lets change the colour of the items view, by changing the background-color in both the header and the body styles, and change the font colour of the header.
Front end item view after CSS change.
As you can see, you can change the look and feel to suit the colour scheme of your site. Obviously I don’t recommend the above colours, they are just to demonstrate how different you can make the auction listing with just some minor css changes.