you can do it using j-query the following way
$("#button_background").css("color",'blue')
you can do it using j-query the following way
$("#button_background").css("color",'blue')
While you can do that there is easier ways to do (check here and here), for example:
using the class selector you can filter all objects that have the "old" class $( ".oldClass" )
and manipulate what classes they have (instead editing the class) :
filter and add the new class
$( ".oldClass" ).addClass(".newClass")
and remove the old class
$( ".oldClass" ).removeClass(".oldClass")
you can also use .css to change a property :
$( ".oldClass" ).css("background","#ff0000")