How to get the median value of a set of data?

I am currently making a program which needs to evaluate colours received from a webcam input, to evaluate if, say, the currently introduced colour is within the RGBA limits of a previously defined green.

The function converts the image received from a webcam into a ImageWidth*ImageHeight length struct, through the GetPixels32() function. From here I evaluate based on 25 pixel values in the area that I wish to detect the colour introduced.

To avoid problems with Salt'n'Pepper noise, I would wish to be able to do this using a median value function, instead of merely going by mean values, but have found no reference as to how to do this.

The way I find the mean value, here shown using pseudo-code instead of actual code (to avoid a lot of confusion my values might cause), looks like this;

 webcam.GetPixels32[ImageValues];
 
 For (int i; i < 25; i++){
 
 RedValue += ImageValues[i].r;
 GreenValue += ImageValues[i].g;
 BlueValue += ImageValues[i].b;
 AlphaValue += ImageValues[i].a;
 
 }
 
 RedValue = RedValue / 25;
 GreenValue = GreenValue / 25;
 BlueValue = BlueValue / 25;
 AlphaValue = AlphaValue / 25;

Any reference to how a median value might be found would be much appreciated.