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