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