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