Control the strength of colour

Blogger insisted on adjusting the exposures when I uploaded these pictures and so each photograph looked exactly the same for some reason.  Blogger has done this before but rectified itself when I re-uploaded the images but this time it stuck to its incorrect guns.  I have therefore provided a link to my site where the colours and exposures will be preserved as they are for certain.

Take 5 photographs: Find the average meter reading and then start at one stop brighter than the original then stop down by half each time.  Apart from the fact that the five photographs vary from over-exposure to under exposure what difference is there in terms of the colour?

As well as the different exposures what I have noticed is the tone of the colour.  The overexposed photograph looks much pinker, almost peach, and the darkest one loses its luminosity.  I prefer the darker two at the beginning of the sequence as they seem much richer and the red is more robust.

Once thing that puzzled me with this exercise (and perhaps I'm going to look like a twit here) but my camera, like most, goes up incrementally in thirds rather than halves (I'm pretty sure).  I could not for the life of me find a way to change it in the camera to halves although I know you can in the light meter I own and carry around and rarely use. Also, when I looked in the course folder at the example given they were thirds with two missing from the sequence - f.5 and f7.1.  So I was a bit confused by this.  I have re-looked at f stop values online and wonder if I'm missing something. 

Please click here to see five exposures of the same coloured subject 
Please click on the small i underneath each image for settings information