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