When you start ROOT from commandline, it will execute the script rootlogon.C in the same directory. This may be useful when you want to load your own classes into ROOT or want to set some styles.
Create a file named rootlogon.C (note the capital C), open it and write
{
gSystem->Load("libAnaClasses.so");
gROOT->SetStyle("Plain");
}
which will automatically load your library libAnaClasses.so into ROOT and set the color of your canvas to white.