Highlight only those dropdowns where the value is not selected.

Highlight only those dropdowns where the value is not selected.

Hi,

I have multiple dropdowns in one of the page, when the user doesn't select the dropdown value, I should highlight those dropdowns only on save.  I am using coldfusion, Javascript and Jquery. I have defined the same class name to all the dropdown fields and there are different id's for all of them. Highlighting the text field works but not the dropdowns.
I'm using the below code for text fields
$('.MandatoryVTxt,.MandatoryVDD').each(function(){
if(this.value.length==0 || this.value==0){
t=t+1;
$("#testingVehicleForm #"+this.id+"").css("background-color", "#F6CED8");
}
else{
$("#testingVehicleForm #"+this.id+"").css("background-color", "white");
}
$(window).scrollTop(0);
});
Also, tried   the below
$('.select2-selection').css('background-color', "#FFFF00");     
I get all the dropdowns highlighted, is there any way i can get only those dropdowns highlighted where the user doesnt pick a value from it.

My dropdown list is generated using

generateDropDownList_kv("DropDown","getContact","testingForm","CONTACT",0,"-Select-" ,false); 
$('#testingDynoForm #VEHICLE_CONTACT').select2();       
Please suggest.