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