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