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)(11,15)(12,13)(14,16)(17,18,21,22)(19,20,23,24)(25,26)(27,33)(28,32)(29,30)(31,35)(34,40)(36,39)(37,38)(4,8)(6,7)(9,10)(11,15)(12,13)(14,16)(17,19,21,23)(18,20,22,24)(26,29)(31,33)(32,38)(39,40)(2,3)(6,7)(10,13)(14,15)(18,22)(19,23)(25,27,30,35)(26,31,29,33)(28,36,37,34)(32,40,38,39)(1,3,5,2)(4,7,8,6)(9,10)(11,14)(12,13)(15,16)(17,18)(19,20)(21,22)(23,24)(25,28)(26,32)(27,34)(29,38)(30,37)(31,39)(33,40)(35,36)(1,4)(2,6)(3,7)(5,8)(9,11)(10,14)(12,16)(13,15)(17,20)(18,19)(21,24)(22,23)(25,29,30,26)(27,31,35,33)(28,32,37,38)(34,40,36,39)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.