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