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