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