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