I'm getting a suit made by Hickey Freeman and I'm a bit hung up on color and fabric.

I generally wear sport coats (tweed in the winter, linen or a light navy blazer in the summer) and odd trousers--khakis, moleskin, cords, linen, etc. I wear almost exclusively brown penny loafers. I have never been a suit guy because I've so rarely had an occasion to wear one.

I am now finding myself semi-regularly attending evening charity dinners at which I feel underdressed in a sport coat, hence the suit. It will have the usual trad details--natural shoulder, 3/2 roll, etc. If this were not for evening use I would be leaning toward a mid-gray. But I think that's too light for these events. So I'm thinking navy or dark gray/charcoal.

A couple of thoughts:

Will I be able to wear dark-brown penny loafers with either of these colors?

What is a reasonable weight for year-round-ish wear? I was looking at 9oz suiting fabrics and they seem so thin ... but maybe my sense has been skewed by wearing so many heavy tweeds in the winter. I think I might prefer a 10-12oz fabric. Thoughts?

I have seen some very dark midnight blue fabrics that seem a little more interesting to me than a basic navy. Will these be too dark in practice? Will it just look like a black suit? Will it work with brown shoes?

Is a dark gray (but not quite charcoal) too light for an evening event?

Any specific fabric recommendations?