This is most likely due to the lighting in the scene.
This lighting mixes with the colour of the textures and you get slightly changed colours.

If you use the draw to texture mode, you already have the texture and you just need to save it.
https://infinity-code.com/doxygen/onlin … a4905147d2

If you are using the Tileset control, before capturing a screenshot of the map, you need to turn off the lights in the scene, and set Environment Lighting Source - Color, Ambient Color - White.
https://docs.unity3d.com/ScriptReferenc … tings.html