Make Black background transparent or white

[James Holmes]

How do you change the background color or make it transparent?

[sallyanne]

Select the fuzzy select wand and click on the background, grow your selection by one pixel and to make sure you have it all selected if you enlarge your picture quite a bit (4 - 800%) and add to your selection, all of the selection should be affected when you colour to alpha then colour to alpha it with your background colour NOT WHITE.

Also you will need to save/export your picture as a png, as jpg's do not support transparency.
EDIT: If you just want to change the background colour to another colour apart from transparency, make it transparent first as above and then add another layer - fill it with the colour you want. Put it below your picture then merge. If you want you can save this one as a jpg

[PixLab]

For this very tiny image a Color to Alpha is not only enough but you have a transparent pipette where we need to remove the black, especially on the top, thus it's the tool to go with.
in the main menu go to Colors ➤ Color to Alpha... a window dialog opens, click on the colored bar to change the color to black..., BG is now transparent ➤ the translucent pipette will also be semi transparent as it should be (not much black in the hand, thus the hand will stay opaque, if problem use the 2 sliders below the colored bar to fine tune)

   

Once it's done, to have a different colored BG, just create a new layer underneath and fill with the color you wish (look at the top of the pipette, it's the right color)