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