I assume you want to store the preference and take action based on that. Try something like this:
// Event-independent color change function
var bblue = function() {
$("dl").addClass("bbluebg");
$("dd .button").addClass("buttonb");
$('.button img').attr('src', $('.button img').replace("White","DBlue"));
}
// Click action
$(".bblue").click(function () {
// Change the color
bblue();
// Store the preference
$.cookie("color", "blue" , { expires: null, path: '/' });
});
// On page load
$(document).load(function() {
// If they chose blue before, change the color
if ($.cookie("color") == "blue") bblue();
});