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