GIMP Version: 3.0
Operating System: Linux
OS Version: Debian 12 + Lxde (desktop)
GIMP Experience: New User

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It is said that blue + yellow = green.
Create new layer with blue color and add new layer with yellow,merge them ,the color don't turn to green,it is yellow.

How can get green color from blue and yellow in GIMP?

The short answer is you can't. Perhaps you are looking at a typical CMYK explanation https://en.wikipedia.org/wiki/CMYK_color_model where overlapping yellow / blue = green.

Gimp is strictly red - green - blue ( RGB ) If you look at yellow you find it is made up of red and green To get to green from yellow you need to subtract red and (obviously) there is no red in blue.

For the sort of image you show, you need a layer of red in subtractive mode, and position does matter, yellow above blue.