When looking at the galaxy, the foods you choose are based on how long you'll be outside. So here are my suggestions.
Snack Foods
If you're only going for a little bit, all you need is a light snack. The most fitting and easiest would be Lucky Charms. With its shooting stars and many colored marshmallows, the galaxy is truly embodied in this iconic cereal.
An easy snack to prepare with Lucky Charms can be found here.
If you have a little more time, here are the amazing pancake cups pictured above.
Another route you can go is Star Wars related, and a compilation of famous movie franchise themed snacks can be found here.
Light Meals
If you have a little more time to gaze at the stars and be reminded of how small we really are, a light lunch that you can still eat while wandering is in order. There are several multicolored foods you can prepare that can be easily slipped in a bag and carried around.
Carbs are great when you need to replace some of the energy walking and wondering took out of you. Try this recipe for some delicious multicolored bread.
Smoothies are also good to carry with you, and the more colorful they are the more diverse their nutrients are. Here's a good rainbow recipe.
Sit-Down Picnic
If you plan on staying at the park for more than a few hours, you may want to pack an entire meal. You want to choose something not too messy, so that when you're looking up and pointing at different constellations, you don't have to worry about making a mess.
A formative guide to a perfect sandwich can be found here.
If you have to prepare food with ingredients from your dining hall, here's how to make some great breakfast sandwiches.
If you have a little more time and a kitchen, you can make these dorm-compatible meals as well.
And finally, for a meal for under the stars, you have to finish off with the classic galaxy donut.
The galaxy is an awe-inspiring thing to look at, so always make sure you have awe-inspiring foods to munch on when you visit somewhere where the stars are clear and bright.