.popup input,
.popup-wrapper input,
.modal input,
input[type="email"] {
    color: #000 !important;   /* Change black to whatever color you want */
}/* Add your CSS code here.

For example:
.example {
    color: red;
}

For brushing up on your CSS knowledge, check out http://www.w3schools.com/css/css_syntax.asp

End of comment */ 

