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