I am considering getting some black overalls
Attaboy!
I've used black overalls for years. Good for hiding dirt, like you I think overalls look far better than jeans and T-shirts, they're easier to work in - much free-er going up ladders than jeans, in the summer all I have underneath is pants and maybe a T-shirt, in winter I have longjohns and thermal vests, in the really cold weather I have a fleece hooded top inside as well, loads of pockets, you look business-like etc, etc.
Having said all that, I'm considering getting us black cargo pants and polo tops for this summer, but that's still to be decided.