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)(11,15)(12,20)(13,14)(16,21)(17,19)(18,23)(22,24)(26,32)(27,29)(28,37)(36,40)(3,7)(5,8)(9,10)(11,17)(12,20)(13,14)(15,19)(16,21)(18,22)(23,24)(25,26)(27,33)(28,30)(29,39)(31,32)(34,37)(35,40)(36,38) involution — undirected(1,2)(3,5)(4,6)(7,8)(10,14)(15,17)(16,20)(22,23)(25,27,31,29)(26,33,32,39)(28,35,37,38)(30,40,34,36)(1,3)(2,5)(4,7)(6,8)(9,11)(10,15)(12,18)(13,19)(14,17)(16,22)(20,23)(21,24)(25,28)(26,34)(27,35)(29,38)(30,32)(31,37)(33,36)(39,40) involution — undirected(1,2)(3,5)(4,6)(7,8)(9,12)(10,16)(11,18)(13,21)(14,20)(15,22)(17,23)(19,24)(25,29,31,27)(26,33,32,39)(28,38,37,35)(30,40,34,36)(9,10)(11,15)(12,16)(13,14)(17,19)(18,22)(20,21)(23,24)(25,30,31,34)(26,28,32,37)(27,36,29,40)(33,38,39,35)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.