Ways to Use Military Shirts

Hi, I live in Phoenix an there’s a need for lighter clothing (as you can imagine); however,there are situations in which I have to be wearing a tie or a bow tie (in a between-formal-and-casual way). Is it acceptable to wear ties with military shirts? I know these are casual shirts, and we are allowed to wear colorful ties (bow tie, skinny tie or regular). Thank You!

Tie Color Recommendation for a Groom

My sister is getting married and her future husband refuses to wear a Tux and a bow tie, he wants to wear a black suit, a white shirt and and tie.

What color tie should he wear? I was thinking of suggesting him to wear a black tie. What other options there are for this formal event?
He is white and has blue eyes and dark hair.

Here in Romania we have a triple part wedding: City Hall (in the morning – close family only), Church (in the afternoon – extended family + some friends) and Reception (in the evening – all the guests), should he wear the same color tie for all these tree parts of the wedding?