Why Do 727's Have One Red Window?

Hey, I'm not sure whether its been asked before, but I've always wondered why some aircraft have one cockpit window painted red?
http://www.airliners.net/photo/Zero-G-( ... ernational)/Boeing-727-227-Adv(F)/1809403/&sid=263107c95d5862747d056f2ce1e74afe
I've seen it on alot of 727's, like the picture above. Its always the second window on the right side. Is it some sort of escape window or something?
Thanks, I would love to know, its always interested me.
Connor
http://www.airliners.net/photo/Zero-G-( ... ernational)/Boeing-727-227-Adv(F)/1809403/&sid=263107c95d5862747d056f2ce1e74afe
I've seen it on alot of 727's, like the picture above. Its always the second window on the right side. Is it some sort of escape window or something?
Thanks, I would love to know, its always interested me.
Connor