Alright, I'll start off by showing my restored house numbers, and part 2 will be just a photo montage of other old house numbers in town.
After I finished cleaning up the plaque and removing paint smears, dirt, and even some previous repairs (someone had repainted the chipped portions in black), I was left with this:
You can clearly see the "blue over white" enamel around the edges, as well as the corrosion.
I'm a bit hesitant to give away all my trade secrets, but in the next step, I went over the metal with a clear product to seal it (yes I'm being vague on purpose). After this, I started colour matching the blue.
The problem with the blue is that it's NOT BLUE. It's indigo. It you look at it under good lighting, it's rather purple.
I wanted to use enamel (oil) paints for the touch-ups, since they are more durable, but FINDING THEM was insanely difficult. I had a few on hand, but some of the colours I needed (dark blue) was all dried out. I went to about 5 different stores and I couldn't find them. Michael's (art supplies) was my absolute last stop (and the farthest away), and I found exactly what I wanted.
My colour match was a mix of blue and red, but it turned out a bit darker than what I wanted. It's still very close, but it could have been better if I had spent more time on it. After the paint dried, I went over the entire thing (front and back) with a clear coat designed for car paint (since it won't yellow).
This was the finished product. Not perfect, but WAAAAAY better than before. I also painted the heads on 2 brass screws to mount it.
Unfortunately, the rest of the porch still looks rather ghetto at the moment, but here's how it looks. You'll notice that I mounted the numbers centered ABOVE the door, rather than poorly tacked ONTO the door mouldings.
This photo set shows the full transformation: