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)(19,22)(20,23)(21,24)(25,26)(27,32)(28,34)(29,35)(30,38)(31,33)(36,40)(37,39) involution — undirected(1,2,5,6)(3,7,8,4)(10,15)(11,18)(12,20)(22,24)(25,27)(26,32)(28,31)(29,36)(30,37)(33,34)(35,40)(38,39)(1,2)(3,7)(4,8)(5,6)(11,18)(12,20)(13,16)(17,23)(26,33)(27,28)(29,39)(30,40) involution — undirected(2,6)(3,8)(9,11)(10,16)(12,21)(13,15)(14,18)(17,22)(19,20)(23,24)(25,28,31,27)(26,34,33,32)(29,36,39,38)(30,35,40,37)(1,3)(2,4)(5,8)(6,7)(9,12)(10,17)(11,19)(13,22)(14,20)(15,23)(16,24)(18,21)(25,29,31,39)(26,35,33,37)(27,36,28,38)(30,32,40,34)(1,4)(2,3)(5,7)(6,8)(9,13,14,16)(10,11,15,18)(12,22,20,24)(17,19,23,21)(25,30)(26,36)(27,37)(28,35)(29,32)(31,40)(33,38)(34,39)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.