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