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