#text {
width: 150px;
height: 150px;
z-index: 1;
}
#text {
text-align: center;
background: linear-gradient(to top right, black 50%, orange 51%);
}
#text h1 {
margin: 0;
line-height: 150px;
mix-blend-mode: difference;
color: #fff;
}