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