I do not know of any way with the default Gimp tools,
You might be able to use the gmic plugin, http://www.gmic.eu Difficult to say without some indication of type of image you are editing.
Using the bucket tool the amount of fill depends on the threshold setting. screenshots https://i.imgur.com/Zbnyspn.jpg
Using gmic, select-replace filter, a bit more work. Selected colour is color picked from within gmic, same spot as bucket fill tool. Replacement color is whatever you want. Output is replaced colour. The tolerance slider acts the same as the bucket fill threshold but is interactive on the preview. screenshot: https://i.imgur.com/HL3NycL.jpg
You might be able to use the gmic plugin, http://www.gmic.eu Difficult to say without some indication of type of image you are editing.
Using the bucket tool the amount of fill depends on the threshold setting. screenshots https://i.imgur.com/Zbnyspn.jpg
Using gmic, select-replace filter, a bit more work. Selected colour is color picked from within gmic, same spot as bucket fill tool. Replacement color is whatever you want. Output is replaced colour. The tolerance slider acts the same as the bucket fill threshold but is interactive on the preview. screenshot: https://i.imgur.com/HL3NycL.jpg