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