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