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)(26,30)(27,34)(28,31)(32,39)(33,37)(35,38)(2,6)(7,8)(25,26,31,37,29,33,28,30)(27,32,38,40,35,39,34,36)(1,3,5,4)(2,7,6,8)(10,15)(14,17)(16,23)(22,24)(27,35)(32,39)(34,38)(36,40)(1,4,5,3)(2,8,6,7)(9,12,13,21)(10,16,15,23)(11,18,19,20)(14,22,17,24)(25,27,28,34,29,35,31,38)(26,32,30,36,33,39,37,40)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.