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