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