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