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