Thank you indeed.

You get the same thing with melon aphid (Aphis gossypii). As temperature increases the aphid transitions from a green (cool) form to a yellow (hot) form. There are intermediate colors, as in "partly yellow," or "somewhat green," and the aphid has a botchy appearance. There are also many different shades of green, from nearly black to a light grass green sort of color.

Thanks

That's a very common scenario. On tobacco we also have the two morphs of Myzus persicae nicotianae (red and green). The Red morph is better adapted and exhibits higher reproductive rates and survives better than the green morph in conditions of overcrowding. We usually get the green morph at the beginning of the tobacco growing season, but as the season progresses (temperature gradually increasing and nicotine content plus alkaloids also increasing in tobacco), the green morphs disappears and the Red morph increases in abundance.

Thanks for this information

Are you certain it is not Aphis gossypii? These two species look very similar and A gossypii has a very wide host range. 

Myzus persicae also has a wide host range, and is commonly found on peppers.

Yes,  it is not A. gossypii.

Sorry, I was not aware that Myzus persicae also did this. With A gossippi, the changes seemed to be related to the condition of the leaf, or to crowding. As you have probably noticed, you will eventually get both colors even starting with a single female. My colony of A g seemed to move from light to dark and then started to produce more males as the proportion of dark wingless females increased. Maybe the symbiots are changing. The actual pattern of which colors preceded which appeared to vary with the family (where I found them in the field). Maybe the symbiots are changing.  It is a fascinating question. 

Dear All,

Also some endosymbiotic bacteria can cause colour change in aphids

http://science.sciencemag.org/content/330/6007/1102

Thanks for the article.

because of its polymorphism which related to the season and food habit