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