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