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