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