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