flexbox 2, кубизм 100%

.palette div {
min-width: 35px;
min-height: 35px;
}

.palette {
display: flex;
}

.color-olive {
margin: auto;
margin-right: 10px;
height: 150px;
}

.color-yellow {
margin: auto 5px 5px 0;
height: 100px;
}

.color-fuchsia {
margin: 5px 0 auto auto;
height: 100px;
}

.color-aqua {
margin: auto;
margin-left: 10px;
height: 150px;
flex-basis: 50px;
}