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