1. Change theme color by parameter. Add the ‘themeColor’ and ‘themeDarkColor’ when initialize the cart.

    $(function(){
        // Create a basic cart
        var cart = $('#cart').DCAJAXPaypalCart({
            width:600,
            height:400,
            themeColor:'#FF0000',
            themeDarkColor:'#000000',
            paypalOptions:{
                business:'YOU_PAYPAL_EMAIL@email.com'
            }
        });
    });

2. You can also changing the color by editing the dc.cart.css included in the lib folder.