div{
    width: 50%;
    height: 100px;
    margin: 0 auto 20px auto;
    border: 2px solid black;
    box-sizing: border-box;
    background-color: orange;
}

.d1{
    transition: width 4s linear 0s;
}
.d2{
    transition: width 4s;
}
.d3{
    transition: width 4s linear 0s, background-color 2s;
}

.d1:hover, .d2:hover, .d3:hover{
    width: 100%;
}
.d3:hover{
    background-color: blue;
}