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