Thanks to everyone who has replied to my question
On behalf of what the plugin would need ( and i really aprecciate if it existed) for myself i say, that it let you put either forms or numbers on color so that you can easily see the difference between them, either if you have to put the numbers pixel by pixel or if the plugin let you identify an RGB code and automatically when placed the pixel name it with the number, doesnt matter, both of the opcions would really help.
I started thinking of this when i could barely see the difference between a yellow and a pastel yellow tone on paint.net, and that got me thinking that, even if my eyesight is good enough to see the difference, eyesight should not be a issue when trying to identifying the colors, for me, in order to place them on a perler work.
Once again, thank you for everyone replies, i would really love is there was a way to make this on Paint.NET and if in the future a plugin is made for it, please, let me know on this post.
Edit: i have found a page (https://www.stitchfiddle.com) thats actually super accurate of what would be great on paint.net, in it, if you select "'Cross Stitch'' then "'No preference'' and finally "Create my own design" you will enter a page with a grid that let you put color squares in order to create a pattern, if you go to the color patellete simbol, you will enconter options for colors, such as naming the color, the count that you have putted on the pattern and finally, an option to edit the simbols so that every square with that color can have the same symbol.