[Gimp-user] Converting from indexed to RGB modes; brush color off

[Maxomega <forums gimpusers com>]

So I was editing a sprite sheet for a video game character, and after working
with it for a bit, I noticed the color I was using was off from the brush color.
Later, I noticed the layers were behaving strange, and that it probably had
something to do with being in indexed mode.

I changed the image to RGB mode, but my brush color is still off, and layering
multiple brush colors combines the colors for some reason. My brushes are at 100
hardness and 100% opacity, so I don't know what the issue could be. I'm just
trying to paint over all the color in the image to be 00FF00, or the greenest
green.

First attached is a screenshot of the base image, unpainted. Also included is
the brush color, which already doesn't match the outside. Note that the top
layer is the active one.

Second attached is what happens when I try to draw over the image with a plain
green brush. The black rectangle is the boundary of the middle layer, but I'm
not sure why it's black at all.

Third attached is what happens when I try to do same thing (painting with the
green brush), but with the second layer active.

I'm just really confused. I don't know much about GIMP, but I've been using it
for well over 5 years and I've never come across something like this.

Attachments:
* https://www.gimpusers.com/system/attachments/1316/original/Capture.PNG
* https://www.gimpusers.com/system/attachments/1317/original/Capture2.PNG
* https://www.gimpusers.com/system/attachments/1318/original/Capture3.PNG

-- 
Maxomega (via www.gimpusers.com/forums)