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