Hi There,
To change the subscribe button color, the code would be:
/*Subscribe button default color*/
input[value="Subscribe"] {
background-color: red;
border-color: black;
color: white;
}
/*Subscribe button hover color*/
input[value="Subscribe"]:hover {
background-color: black;
border-color: red;
}
You can get a color hex code here.
And you can learn more about CSS properties here.
Hope it helps,
Cheers!