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)(11,19)(12,16)(13,17)(14,18)(15,21)(20,24)(22,23)(25,26,30,31)(27,35,37,32)(28,29,34,33)(36,39,40,38)(9,11)(10,15)(12,20)(13,22)(14,21)(16,23)(17,24)(18,19)(25,27)(26,32)(28,36)(29,38)(30,37)(31,35)(33,39)(34,40) involution — undirected(2,5)(6,8)(9,12,14,13)(10,16,18,17)(11,20,21,22)(15,23,19,24)(26,31)(27,35)(29,33)(32,37)(36,38)(39,40)(1,3,4,7)(2,6,5,8)(9,12,14,13)(10,17,18,16)(11,20,21,22)(15,24,19,23)(25,28)(26,33)(27,36)(29,31)(30,34)(32,39)(35,38)(37,40)(9,13,14,12)(10,17,18,16)(11,20,21,22)(15,23,19,24)(25,29,30,33)(26,34,31,28)(27,36,37,40)(32,38,35,39)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.