Someone in a townhouse not far from here got solar panels, for free. The
electric meter is in the front and that's why they ran 1.5 or 2" conduit
up the front of the house to the roof, and put in a 3" long junction box
where the conduit had to bend almost 90^ to go on the roof.

I think it's uggggly.

What should they have done differently, even if the homeowner had to
pay?

Can conduit be painted and how long would it stay approximately the same
color? Is there any conduit or useable alternative that is already
colored? White? Brown? Mariner turquoise?

Even that wouldn't be very good but it's the easiest most obvious.

How is it properly done when put on a roof?

Down through the stack to the basement, I presume, and the electric
connections and the solar control box (2 or 3 times the size of the
meter) are put in the basement????