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