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