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