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