One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(3,8)(4,6)(5,7)(11,15)(14,16)(17,18)(19,20)(21,23)(22,24)(25,26,30,31)(27,34,33,29)(28,32,36,39)(35,37,40,38)(1,3,5,4)(2,6,7,8)(9,10,13,12)(11,14,15,16)(17,19)(18,22)(20,23)(21,24)(26,31)(27,33)(28,36)(37,38)(17,18)(19,20)(21,23)(22,24)(25,27,30,33)(26,29,31,34)(28,35,36,40)(32,38,39,37)(1,4,5,3)(2,6,7,8)(9,11)(10,14)(12,16)(13,15)(17,18)(19,22)(20,24)(21,23)(25,28)(26,32)(27,35)(29,38)(30,36)(31,39)(33,40)(34,37)(1,2)(3,6)(4,8)(5,7)(9,12,13,10)(11,16,15,14)(17,20,21,22)(18,19,23,24)(25,29)(26,33)(27,31)(28,37)(30,34)(32,35)(36,38)(39,40)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.