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