Phenomenal game \( ^0^)/
I really enjoyed playing, everything was simple to understand, yet still challenging enough to create an engaging experience. I loved the artwork, the music was very fitting and calming, and the whole idea of serving sandwiches to aliens is so original and humorous. I noticed in the comments that others had mentioned my only major concern: that being the difficulty in differentiating certain ingredients. I agree with them that the colors play a role in the difficulty, but also the shape language; I believe that the colors were perfectly fine, as long as the shapes are still unique enough.
If you do see it as more fair to the player if you make the colors different, I think another fun way to increase the challenge would be for customers to change their orders while you're making it. For example, once you put on the meat, they customers thought bubble could change to an ellipses or maybe a "wait!" for a moment, then change back so that all the ingredients you had placed so far are the same, but now the next ingredient you need to place is olives instead of peppers or something. It would keep players on their toes, it could become more common as the days progress to increase the difficulty, and it's kind of funny because people do that in real life. It's just a suggestion though, so do with it what you will.
Overall, great job on making a great game! :D