Add border/background color/color text of embedded pop-up [closed]

Simple CSS Styling

Add this to your CSS

 #mc_embed_signup {
    background:#000;
    color:fff;
    border:1px solid red;
    padding:20px;
    }

Adjust to Your Preferences

You can adjust the border width by giving it a larger than 1px value, such as this:

border:8px solid red;

These are the colour values used. They are called Hexadecimals (Hex):

#fff = White

#000 = Black