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