Here is how I did this using the css clip-path
property alongside relative and absolute positioning to create a more fancy cross.
.cross {_x000D_
width:150px;_x000D_
height: 150px;_x000D_
border: 2px solid #555;_x000D_
border-radius: 5px;_x000D_
position: relative;_x000D_
background: #efefef;_x000D_
}_x000D_
_x000D_
.cross .diag1{_x000D_
position: absolute;_x000D_
width:100%; height:100%;_x000D_
clip-path: polygon(90% 0, 100% 0%, 10% 100%, 0% 100%);_x000D_
background: #311B92;_x000D_
}_x000D_
_x000D_
.cross .diag2{_x000D_
position: absolute;_x000D_
width:100%; height:100%;_x000D_
clip-path: polygon(0 0, 10% 0, 100% 100%, 90% 100%);_x000D_
background: #1B5E20;_x000D_
}
_x000D_
<div class="cross">_x000D_
<div class="diag1"></div>_x000D_
<div class="diag2"></div>_x000D_
</div>
_x000D_
Here is a link to the code on codepen if you'd like to tweak it.