Change an sgv background with an if statement

would you help me with this: I want to change the background of a DIV based in the score.

if (score>=4 ){
    document.querySelector("#babyState1").classList.add("hidden");
    document.querySelector("#babyState2").classList.remove("hidden");
    
    
}
else if(score>7){
    document.querySelector("#babyState3").classList.remove("hidden");
    document.querySelector("#babyState2").classList.add("hidden");
}

else{
    document.querySelector("#babyState1").classList.value="";
    document.querySelector("#babyState2").classList.value="";
    document.querySelector("#babyState3").classList.value="";
    document.querySelector("#babyState2").classList.add("hidden");
    document.querySelector("#babyState3").classList.add("hidden");
}