The solution you posted works but only if the client uses the EFW as it's DNS server.
If your clients are using another DNS server on the GREEN/ORANGE/BLUE zone e.g. Active Directory DNS server, then I think you will need to enter the host in that DNS server also.
Not entirely true. What you can do is to add endian firewall as your 1st DNS forwarder on your AD DNS Servers. This way you dont use the Endian DNS directly, but works the same.
Or if your AD domain name = your web domain name you must create a local registry on the AD DNS to point that server by using the local IP.