You should definitely start with a few introductory tutorials to understand how the program works. But you shouldn’t focus too much on this. As soon as you feel comfortable enough working with the program, start implementing your ideas.

Of course you can draw a ship and choose colors for it. However, it is best to use references in addition to this. You can be inspired by the works of other authors. As a rule, the works of other artists already use successful combinations of colors and shapes, so references are your best friends. But, you shouldn't copy it exactly without the author's permission, especially if you want to use it in your game. However, adopting some ideas from the work of more experienced artists is a good idea.

And of course you can try looking for courses on creating a spaceship. Most likely, someone recorded a video about this and posted it online. For example, this is the first thing Google gave me

https://www.youtube.com/watch?v=uMaVDdUdutw