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