Q. My colleague, a non-Jew is getting married to another non-Jew next month. So far, I’m not invited to the wedding since I just started a couple of weeks ago.  Should I do anything to acknowledge the event or just say congratulations and leave it at that.

A. It is definitely not correct to attend the non- Jewish wedding ceremony even when not done at an other religion’s temple, as when celebrated at a garden or a wedding hall, since likely one would be listening to antagonistic views to our fate.

As far as just blessing them is concerned, since there are variants dealing with their marriages, there are different views by Poskim as to what should be the accepted ceremony.
Indeed, your best option is just to give congratulations and if proper send a gift. Rabbi A. Bartfeld as revised by, Horav Dovid Pam, Horav Aharon Miller, Horav Chanoch Ehrentreu and Horav Kalman Ochs Shlit’a