Filll different colors

Hi ,

Sorry for asking such a trivial question on this forum! 

  I am making a plot where I want to divide it into three different region ( vertically ) due to 3 different selection.  I am using a macro to make this plot where I user TGraph to plot points and then join them with simple lines.

  Could someone suggest how to make these three different regions (let say the three regions are :   (x< 3.0),  (3.0 > x<4.5) and fill them with different colors??

Please find the attached macro and .eps file.

Thanks in advacne,
with best,

Sorry the files are here
Result.C (1.37 KB)

.eps file