The blue text refers to a VT100 terminal control code. Back before mice and graphics, people talked to big computers using terminals, usually a CRT and a keyboard that connected to the computer and acted as a remote interface. They sent characters back and forth, and usually, the characters sent to the terminal would be directly displayed to the user. However, the VT100 (and its compatible successors) could interpret some sequences of characters as special commands. A common one is Ctrl-H which would ring a bell on the terminal. The one in blue is the code to move the cursor back to the top left of the screen, or the "home" position.
Add that to the riff on the "if you lived here, you'd be home by now" signs that show up on apartment complexes, and you've got one of the geekiest things that you could possibly wear. Also in the running is the C programmer's reference shirt I once had which had all the text printed upside down so you could look down and read it while you were coding, and the KMFMS shirt that parodies the art style of the industrial music group KMFDM while also taking on Bill Gates.