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