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