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