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)(11,15)(12,13)(14,16)(17,18,21,24)(19,22,20,23)(25,26,30,31)(27,28,35,32)(29,37,38,33)(34,40,39,36)(4,8)(6,7)(9,10)(11,15)(12,13)(14,16)(26,31)(28,32)(29,38)(34,39) involution — undirected(2,3)(6,7)(10,13)(14,15)(17,19,21,20)(18,22,24,23)(25,27)(26,32)(28,31)(29,39)(30,35)(33,36)(34,38)(37,40)(1,3,5,2)(4,7,8,6)(9,10)(11,14)(12,13)(15,16)(17,18)(19,22)(20,23)(21,24)(25,28,30,32)(26,27,31,35)(29,36,38,40)(33,34,37,39)(1,4)(2,6)(3,7)(5,8)(9,11)(10,14)(12,16)(13,15)(17,20,21,19)(18,23,24,22)(25,29,30,38)(26,33,31,37)(27,34,35,39)(28,36,32,40)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.