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