Detect the green color in an image

Hi, I am trying to detect the green color in an image. PLease could anyone help me?

[Merged information from duplicate question]

I have colour image of plant that contains plant, pot and soil. I tried to segment just the green leaves of plant by using hsv colour space then take the image histogram of each space but I dont know how can I benefit from image histogram function in Matlab. Can any one help me please?