Re: How do modify color on an WEB page Element, using APPBuilder

try

Output.$().css('background-color", '#0F0'); // background

or

Output.$().css('color", '#0F0');  // color of text

or

$('#' + Output.getId()).css('background-color", '#0F0'); // background

or

$('#' + Output.getId()).css('color", '#0F0');  // color of text

-D