Submit button style

Go to Plugins–>Editor–>Select Contact Form from Dropdown–>Select CSS file.

Call submit button like this:

#cntctfrm_contact_form input[type=submit] {
    here goes your styling. I´d make sure this one down here is in it:
    cursor: pointer;
}

#cntctfrm_contact_form input[type="submit"]:hover {
	background: #??????;
}