Look at the Fig. 2.1, in acroread the colors are wrong (very saturated), while they are ok with other viewers... This problem occurs with all png images included in a latex file.
In fact, it happens only with png with alpha channel.
But I heard it's normal because the pdf version is 1.4 so <1.5... Strange, because it works with other viewers...
I have to find how to make a pdf 1.5 with pdflatex...