>change the Pop up background color and Text color?
like any colours, sizes, texts etc etc just use css.

>there is an email section after
as it says in that screen:

Add your Post/Zip codes (Distance) as required by entering it into the relevant field.
Enter an email address (multiple separated by comma) the order should be sent to when this Post/Zip code is selected by the client or leave empty to send it to the email address defined in your general wppizza->order settings.
Set delivery charges and free delivery amount applicable to this Post/Zip Code, enable and save. Charges set will be applied according to your delivery charges settings in wppizza->order settings->delivery charges and – of course – depending on the selected Post/Zip Code by the User.

use your browsers element inspector to find out which element has which class/id