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