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