Element identification for CSS of hover button wdf_send_donation

Not related to a problem or suggestion with the plugin itself, but I cannot seem to figure out the element name and necessary CSS to affect the wdf_send_donation input.

For example, in order to make the button red and I try:

wdf_send_donation input {
color: red;
}

or even

input.wdf_send_donation {
color: red;
}

Nothing works, and I'm certain it's because I need to specify in CSS whether it's in the hover, active, or default condition. What is the correct CSS for each of these three conditions to apply to wdf_send_donation?