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