I don't know what OS/X's terminal emulator does with colour on tabs, but if using GNU
xterm, you could add something like:
hardstatus string '%D %d %M - %c - %h (%n)^G^11;TekHVC:%n10/80/20'
~/.screenrc to have a different background colour in every
screen window/tab/pane (however you want to call them).
screen displays the hard status in the xterm title bar by outputting something like:
Above we set blah to include
%n is expanded to the window number so for the first window, it becomes:
\e]11;...\a is the xterm escape sequence to set the background colour. It supports various colour specifications, those supported by
XParseColor from the X libraries. The
TekHVC:Hue/Value/Chroma one, where
Hue takes values from 0 to 360 (and wraps) allows us to select a different colour for each window (10, 110, 210, 310, 410 (aka 50), 150, 250...)