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