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