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