I lightened some human hair extensions using only 4o developer creme, no bleach. I'm not a colorist either and had no experience whatsoever with coloring so I did not want to use bleach or anything complicated like that. I was able to lighten the hair from a 1b to about a #4 . I checked it about every 2 hours until it got to the shade I wanted.
You basically saturate the hair with developer , wrap it in foil and put it in a warm place. It was summertime when I did it so I sat the packet out in the sun. When the sun went down I put it in a warm oven. I don't think warmth is required , it just speeds up the process. It's a slow, very safe way to lift the color. There are a bunch of YouTube tutorials on it. Here is one:
