The Gateway address for your clients is the green interface. The gateway address for your red interface has to be the address of the isp router. For the green interface you don’t have to set a gateway.
Please have also a look here:
Internet access for client connected to NS - #2 by robb[quote=“Loboexe, post:1, topic:8664”]
Can I add this to my GREEN LAN with a fixed IP without any special configuration needs
[/quote]
What you want to do with these clients, only Internet?