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