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