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