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