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