html link tag color not changing after clicked

Link color not changing after i clicked. I used side navigation bar css style with links. Here is my css styling:

i tried with active but still not working.

.sidenav 
{
height: 100%;
width: 200px;
position: fixed;
z-index: 1;
top: 0;
left: 0;
background-color: #06799f;
overflow-x: hidden;
padding-top: 20px;
}

.sidenav a 
{
padding: 15px 20px 4px 18px;
text-decoration: none;
font-size: 25px;
color: #f1f1f1;
display: block;
}

.sidenav a:hover 
{
color: #000000;
}

.sidenav a: active
{
color: black;
}

@media screen and (max-height: 450px) {
.sidenav {padding-top: 15px;}
.sidenav a {font-size: 18px;}
}  

expected: is the change of link color when cliked