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