You should give .fb5 a second repeating-linear-gradient in the background property

.fb5 {
width: 10%;
height: 33%;
background-color: var(–building-color2);
position: relative;
right: 10%;
background: repeating-linear-gradient(
90deg,
var(–building-color4),
var(–building-color4) 10%,
transparent 10%,
transparent 15%
),
repeating-linear-gradient(
90deg,
var(–building-color4) 0%,
var(–building-color4) 12%,
var(–window-color4) 12%,
var(–window-color4) 44%
);
}

Please edit your post and add the step link