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