In my head cannon, Starfleet had saucer shaped ships like the saucer from Forbidden Plant (the C-57D). That’s why the saucer section of this ship has three landing legs and its own shuttle bay with a door at the rear of the saucer section. The saucer sections were the entire ship and had to do all the things that you would expect from the later ships that had a saucer section combined with a secondary hull and warp nacelles.
I like Chris Foss’s work. His ships are very colourful and have lots of bold, diagonal, stripes, and checkerboard patterns. On my ship, any opening that has moving parts has bold, yellow and black, diagonal, stripes.
The shuttle bay door is just large enough to launch a single shuttle and there is a pressure curtain to seal the immediate area around the shuttle before the outer door is opened. At the time that this ship was operating there were no magic forcefields to hold in air and it is easier to pump out the air from a small enclosure that it is to pump out a large one. This small enclosure is the shuttle bay airlock.
The roof of the airlock is a door that raises up and slides over the yellow and black striped area so the shuttle craft can be launched or retrieved.
Although I have wasp striped sections because I’m a Foss fan and think that they are kewl… the rationale behind them is that they are a warning for moving parts and places where you shouldn’t stand.
In that spirit, I have warning text around the area and I tried various combinations of arrows, and checker boards, and hexagonal patterns to try to indicate that this part of the hull is a door that slides and that you should keep clear of the area.
The gallery below show some of the things that I tried. I was never happy with any of them.
At one point I hid the door geometry and looked into the airlock. I liked what I saw. The pylons are made of, “space glass”, transparent aluminium or, diamond coated transparent beryllium, whatever. And I thought, “Why try to convey the idea that there is an airlock below here with images? If the door is transparent then you can see what is underneath”
The gallery bellow gives an impression of what it will look like with a glass door.