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