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