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