I colored in an image but the outline is still there...how to get rid of it?

[Ofnuts]

Along the path, you likely have pixels of a color that are far enough from the background to no be taken in account, but still have a significant part of the old background to bee seen as a halo.

Making a guess without seeing your picture: instead bucket-filling "similar colors", make a selection with the path, and bucket-fill the selection, after putting the bucket-fill tool in "Behind" mode.