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