For the text fields (Name, Email, Captcha Code, Security Question): The styles are defined in SpryValidationTextfield.css (Approx lines 46 - 63)
For the textarea field (Comments): The styles are defined in SpryValidationTextarea.css (Approx lines 39 - 54)
Or you could give each field an inline style on the form's page:
<input name="Contact_Name" type="text" class="inputValue" style="width:200px; border:solid 1px #333;" id="Contact_Name" onblur="if . . . etc.