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