Hi all.
So I’m looking for a pixel art editor, specifically with functions to replace colours, count colours and reduce the amount of colours, perhaps by merging very similar colours. Are there any artists out here with recommendations for such an editor?
you can never go wrong with Adobe Photoshop. at least, that’s what i’ve always been using for sprites and i never got issues with it.
the only downside is that it takes time to learn all the features because there’s many of them, and the software itself isn’t exactly user-friendly unless you follow guides and tutorials about specific subjects.
once you learn the basics, it gradually becomes easier to use the more you work with it.
no idea about other softwares, as i’ve only used PS so far.
For my splices, item icons and other sprite stuff, I use usenti. It’s free and it allows you to reduce colours easily. I highly recommend it for making portraits and the like.
Thank you for the recommendations, I will look into these 
While on the topic, a sprite in gba needs to be 16 colours. Does the transparency layer count?
Edit: It seems it does.
yes, it does count, although people normally use a background color for sprites.
not sure if it’s because of engine requirements, or if it’s simply a visual preference.
it’s certainly easier to work on a visible background with color contrast, rather than a transparent one.
Usenti is definitely the way to go for this. It has a quantize function which will do what you want, though your results may vary on how well it reduces the colors on its own. It might be worth using this process only as a base of reference in order to more manually change and reduce the colors to get a better gamut and proportion from the source.
It also allows for setting the palette order too, which can be a useful feature. I might advise taking a screenshot of the palette window and pasting it into another graphics program so that you can zoom in and color dropper if you have several similar shades in the palette, just to make sure you are using or modifying the correct one(s).
@ Fenreir - It’s a little bit of both. The color still exists in the palette, it just isn’t rendered. But, having a background indeed does make it easier to visualize what you’re working on.