hi
I want to detect color of touch pixel on any one layer… " glReadPixels " gives me color of pixel but it consider the whole scene …
in my game their is bg and anther layer on my bg layer … In this case i want to detect color of touch pixel but it leaves bg layer color and gives only upper layer color
its urgent 
I think you should get it by yourself, loop the array and get what you want.
Although many people have asked this very question, I insist that you had better not to judge the RGBA color value from images in opengles games.
glReadPixels is very inefficient. You can change the game logic to other ways.