Can you post a screenshot of what it looks like in-game?
Could it be that your textures are just compressed? Unity imports textures as compressed by default. You have to set it to TrueColor for every image you add to your project.
If you have your project settings with 2D defaults, it might be that your image was imported as a Sprite, which has a hidden flag to "set alpha as transparency" which tends to mess up the image if you use Spine/Skeleton. It makes the colors bleed into the transparent pixels so it might look like there are bands of colors.
In either case, import the image as a Texture, set the format to Truecolor or uncompressed. If that looks a bit too blurry for you, change the Texture type from Texture to Advanced, then UNCHECK "Generate Mipmaps"