HELP! I can't find this simple thing in the manual!

I’m trying to simply change from color to black and white or grayscale,

Did the “select All” finction, bt I cant figure out how to elimiinate color

See here: https://docs.gimp.org/2.10/en/gimp-image-convert-grayscale.html

Two main ways:

  • Colors > Desaturate entries (the simplest being Colors > Desaturate > Desaturate will convert the image to grayscale, but keep it in RGB mode, so each pixel is still represented by 3 colors values and this process makes them equal). This applies to a single layer (within the selection), and you can add colors later.
  • Image > Mode > Grayscale converts the whole image to grayscale (this applies to all layers, and disregards selection) and each pixel is now represented by a single value.

Hi - I’ve covered this topic in an answer on STack Exchange a few years back, describing more than 10 ways of achieving that and the major differences between them: