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