You can always use the image specs tool in the top menu to double check.
If you want to take the lazy way our the save as .gif because you never know what type of .png your app uses and what color profiles. I think your problem is with that kind of thing.
 

Wow, I didn't even know that, when I indexed colors it said that I'm using 22 colors. Thanks a lot, I'll try to do better next time!

You are having technical problem of some kind. It could be your app settings or file output. If you use a pen to pixel then the setting of that could be off too.
Here you actually have 29 colors not 22. For example, you have 4 dark blue colors and there should really only just be 1 blue color, maybe 2 if the 2 pixels on the grey wings were intentional.
Use the forum for help with all this stuff and ask all the questions you need.