What you will need:
In Appdata/Roaming/Sonic3AIR/mods,make a folder,you can name it anything.
Step 2:Open Notepad, and paste this,
}Next,Save it as "mod.json" in the folder of your mod.
Step 3:Go in your main S3AIR folder (the one that has the .exe),and then go in
doc/modding,Copy the folders "sprites" and "palettes",and then paste them into the folder
of your mod.
Step 4:Open GIMP,and then open the .bmp of the character you want to change,and it's palette.
In GIMP open the character sprite file,Go in Windows>DockableDialogs>Colormap (make sure the image mode is indexed,or there will be no colormap.)
You will need to change the colors into the ones that belong to your character,
Make a new file and paste your character's sprite. Copy the colors from your character and overwrite
colors in the colormap. Then paste your sprite.
In the palette file,do the exact same thing except use the pencil to overwrite colors.
All the colors go in a straight X line,the lower lines are Underwater colors and Super colors.
Step 5. When you're done,overwrite both files.
You have sucessfully made a character mod. if there's any problems,ask me on the discord. i'm the uncle joel guy.