Ah thanks so much! Really means a lot that you put it in your reference list, that's so cool! And yeah you're definitely right about your critiques. I wanted to add sound, but I had only like 2 hours left before the deadline and I was EXHAUSTED lol, so I decided to leave it out. I also thought about adding some sort of indicator so that Doge would tell you where enemies were coming from, but I could settle on an idea on how to implement it, but I think you're right that it may have added some extra intensity to the game, so that's good.
Now, for the fun part! The coloring of the game was achieved with two things: 2d Lighting, and Post Processing. The space background for example is covered in dozens of different 2D lights (freeform lights to be specific) to give it a warm colorful feel like in No Mans Sky or something. I also used lights for Doge to make her stand out more. I learned how to do 2d Lighting from youtube tutorials and simple trial and error (I can give you a bunch more info about where I learned it if you want). If you do it right in my opinion, you can make most 2d games look absolutely beautiful with just lights alone, post-processing just adds that extra touch of prettiness to it. I added the post-processing with Unity's URP package: Brackeys has a few videos on it, which is where I learned it from. Unlike the 2d lighting, the URP can be used with both 2D and 3D, its such a wonderful asset that I very well may never make another game without it, seriously its amazing. Some of this may sound complicated, but after you play around with it for a bit, you'll grow comfortable with it and the graphics of your game will see a huge upturn in quality.
If you have anymore more questions just lemme know!!