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