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