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