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