MERRY CHRISTMAS & HAPPY NEW YEAR!

It should read:
Merry Christmas and a Happy New Year.
(the article is missing)

Should we say “[color=red]a good morning”?

As far as I know, you just say “good morning”, without [color=red]a

It was just put in the CAPTION form closing with an exclamation mark.
Anyhow now I wish you a very happy new year.