One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(3,6)(4,5)(7,8)(11,12)(15,16)(17,18,21,19)(20,23,24,22)(25,26,30,34)(27,32,28,31)(29,37,38,33)(35,39,36,40)(1,3)(2,6)(4,7)(5,8)(10,14)(15,16)(25,27,30,28)(26,31,34,32)(29,36,38,35)(33,40,37,39)(1,3,5,8)(2,7,4,6)(9,10,13,14)(11,15,12,16)(17,19,21,18)(20,23,24,22)(25,28,30,27)(26,32,34,31)(29,36,38,35)(33,40,37,39)(1,3)(2,7)(4,6)(5,8)(9,11,13,12)(10,15,14,16)(17,20)(18,22)(19,23)(21,24)(25,26)(27,31)(28,32)(29,37)(30,34)(33,38)(35,40)(36,39)(1,4,5,2)(3,6,8,7)(9,12,13,11)(10,16,14,15)(25,29)(26,33)(27,35)(28,36)(30,38)(31,39)(32,40)(34,37)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.