In my game, if one sprite touches another, the game will be over, so I decided to put in a game over sound effect and some text. However, when I have the sprites touch each other, the game over sound doesn't play.
Here is my script:

when green flag clicked
show
play sound [ v] until done

The first thing that I see is that you have set the sound to operate only at the initialising of the game.
Secondly “Show” is for graphics.

Assuming that you have two sprites of the colors in the script below, then when they touch the sound trigger is activated.

if <color [#11dedd] is touching [#975a8d] ?> then
play sound [tune v] until done
end

Does that make sense? A more experienced Scratcher may find some better explanation.

create clone of [myself v]

Put a forever loop around the if statement.

forever
if <> then

end
end

Like that, but with your collision detecting blocks.

Basically, it is ALWAYS detecting if something is happening. Just put that code under your green flag bit.