Badge.backgroundColor

Description:

The background color for the badge; accepts hexadecimal notation, RGBA, and color name values (e.g., #afafaf, (200, 200, 200, 0), blue).

Example:

//
// The background process (index.html)
//

// Set the button's properties
var properties = {
  disabled: false,
  title: "My Test Extension",
  icon: "icon.18x18.png",
  badge: {
    backgroundColor: 'blue',
    color: '#ffffff',
    textContent: '42'
  }
};	

// Add the button to the browser UI
var button = opera.contexts.toolbar.createItem(properties);
opera.contexts.toolbar.addItem(button);

// Change the background color of the badge with each button click
var i = 1; 
button.addEventListener('click', handleClick, false);

function handleClick() {
  var badgeColor = (i % 2) ? '#5566ff' : '#cc5555';
  button.badge.backgroundColor = badgeColor;	
  i++;
}