[Gimp-user] controlling background color

[Spencer Graves <spencer graves effectivedefense org>]

      How can I control background color?


      I've done File > Open > [a png file with a transparent background].


      This gives me an image with a transparent background.  I need a 
white background.  I try Layer > "New Layer" > White, and the layer is 
NOT white but a teal green that matches one of the colors in the image I 
opened.  Layer > "New Layer" > "Background color" gives me the same teal 
green, which the computer seems to think is white.  Layer > "New Layer" 
> "Foreground color" gives me black, which matches another of the 
colors in the image.  I've tried using the "Bucket Fill" tool with the 
new layer, so far without success.


      The image I'm trying to modify is the logo for the Citizens' 
Climate Lobby, "CCL-Logo-H2.png", which I found by downloading the 
entire web page from their web site (attached, in case your email system 
will support this).  I'm using it in a place with a black background, 
and all the lettering disappears.  See 
"www.kkfi.org/program-episodes/citizens-climate-lobby-carbon-fee-dividend".


      I've tried this with both GIMP 2.10.8 and 2.8.22 under macOS 10.14.2.


      The capability surely exists.  Sadly, my web search efforts and 
experimentation have so far failed to find how to fix this.


      Suggestions?
      Thanks,
      Spencer Graves