It's been 7 days now after my open hernia surgery, and my right testicle is very swell like double it size, is this normal?

Sometimes: swelling of the scrotum or testicle occurs after hernia surgery. More swelling is common if it was a larger hernia or if the hernia was very scarred internally. Sometimes purple discoloration is also seen. This is not unusual & is temporary. Contact your surgeon with any concerns & follow up with them to be sure you are healing properly.

No it is not normal: Some swelling at surgical site and some bruising in scrotum is to be expected. Testicular swelling might mean interruption of blood supply to it. Notify your surgeon immediately.