Select the colour with the eyedropper and then go: Select>Color Range and drag the slider till you have what you want. The Help at the top is a lot of help learning this stuff and really conveniently located at the top of the screen,heh heh heh.. ...

 

Once in a while I look around,
I see a sound
and try to write it down
Sometimes they come out very soft
Tinkling light sound
The Sun comes up again