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