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