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