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