... google? my 1 min worth of googling:
http://www.computing.net/answers/networking/using-cat5e-cables-with-rj11/25780.html
"Although I do not recommend it, but if you want to tinker at your own risk, use the blue pair on CAT5 wired as 4,5, for red and green of RJ11 and use 1,2,3&6 (orange and green pairs) for ethernet. In RJ45 the blue pair corressponds to the 2 center wires of RJ11 (red,green) automatically."
Hope that helps.