background color none

1element {
2	background-color: transparent;	
3}

1div {
2 opacity:25% ; 
3}

1/* To apply color to background you have to use 'background-color' property and value of property is color name. */
2html,body {
3  background-color: blue;
4}

1//javascript type css:
2document.body.style.backgroundColor = "blue";
3// or inline css:
4<div style="background-color: blue;"></div>