So my friend asked me this and I wasn't 100% sure on the answer. Is implantation bleeding just very light in color and…

So my friend asked me this and I wasn't 100% sure on the answer. Is implantation bleeding just very light in color and amount or can it be like 2 days of the brownish/red color? They're ttc and she just had that yesterday and today and she said it just went away within the last hour. She said it was heavier then spotting but lighter than her normal periods and she was just wondering if that could possibly be implantation.