The Product Price is set to 0.00
<br /><br />

The Product Priced by Attributes is set to YES
<br /><br />

The attribute prices are defined without the price prefix of +
<br /><br />

The Display Price is made up of the lowest attribute price from each Option Name group.
<br /><br />

If there had been a Product Price, this would have been added together to the lowest attributes price from each of the Option Name groups to make up the display price.
<br /><br />

The price prefix of the + is not used as we are not "adding" to the display price.
<br /><br />

The Colors attributes are set for the discount to be applied, their prices before the discount are:<br />
White $499.99<br />
Black $519.00<br />
Blue $539.00<br />