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