You can, if it makes a better image. You just seem to struggle with choosing effective colours so far. Limiting yourself can help you learn to choose better colours. Even painters, who work with effectively infinite colours in total, limit the portion of the colour space that they use because it makes a better image. What I am suggesting is that you do the same.

Like I mentioned in my previous comment, think in terms of relative colours. This is useful not only in PA, but NPA as well. It allows you to define the visual mood of your image and create all the "real" colours in terms of it, giving you a more unified image, which is in most cases more appealing and clear than one that's all over the place.

eishiya, thank you! Right now i'm trying to fit into 32 colours palette and i don't like the result much. Maybe i'm wrong, but why can't i use more colours if i have the room for them?

Instead of thinking of colours in terms of "cutting them down", try to think in terms of reuse. What things could share colours? For example, the air tanks on the character's back could be made the same colour as some of the ground, the gloves could be the same colour as the backpack. You can get a lot of mileage of reusing the shadows of some areas as the lighter parts of others, and so on. Two objects don't have to be the same colour to share colours.

Also try to think less in terms of the actual colours of things, and more in terms of relative colours. That will help you reuse colours, and it will help you use more unified colours in general. If you juse colour everything the colour that it actually is, it'll all look like it's not actually existing in the same place.