CentOS 6.0 comes with the ability to set its TERM to
screen-256color. It doesn't work in CentOS 5.7, though.
How can you get CentOS 5.7 to support
If you have a CentOS 6 box handy, you should be able to get the source of the terminfo file for screen-256color and then compile it on the CentOS 5 box.
Take a look at:
I haven't tried it, but something like this:
On the CentOS 6:
Of course, read documentation and man pages, etc.