How to get more Accurate Feathered Edges

[Adap]

I am trying to get my edges of my image to look smoother I'm using feathered edges by 2px and it looks like the the blue one. I want it to look more like the green image but feathering only doesn't seem to work. If I add more than 2px it just looks blurry and any less it barely even changes it. Any suggestions?

[denzjos]

Probably a case of a little difference in selection I think (gimp = pixels). If you want just the same feathering as the green one then there is an easy solution, just make a layer copy from the green one and change the colour to blue.
Colours / Hue-Saturation / Hue

[Ofnuts]

If you want sharp and smooth edges use paths:

   

If you just want the same object in another color, either

• Lock the layer alpha-channel and bucket-fill the layer (no selection necessary) with the new color.
  
• Layer ➤ Transparency ➤ Alpha to selection, add a layer, and bucket fill the selection with the new color.