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