How to color convert a texture before it's time to display with openGL ES

How to color convert a texture before it's time to display with openGL ES

I'm working on a video player (based on openGL ES) for iPhone where the
frames arrive at the renderer at a rate faster than the display rate
(33ms). As the frame arrive I store them and then when it's time to
display a frame, I use an openGL shader to make a color conversion and the
RGB converted image is displayed on the screen. What I would like to do is
to be able to convert the frames as they arrive but I'm not sure how to
proceed. Can some one describe the steps needed to accomplish this? Also
is this necessary, what I mean is it a good practice to do the color
conversion right when the frame is received and only swap the buffers when
the display callback is fired?