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