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