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