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